In the following example, instead of traveling down a vertical line, you can continue along the main path:. If there is a database named oracle2 , then, according to the diagram, all of the following statements are valid:. Loops let you repeat the syntax within them as many times as you like. So, after choosing one column name, you can go back repeatedly to choose another. Read a multi-part diagram as if all the main paths were joined end-to-end.
The following example is a two-part diagram:. The names of Oracle objects, such as tables and columns, must not exceed 30 characters in length. However, if an Oracle identifier is enclosed by quotation marks " , it can contain any combination of legal characters, including spaces but excluding quotation marks.
Whereas a cursor is static, a cursor variable is dynamic because it is not tied to a specific query. You can open a cursor variable for any type-compatible query. To disable a cursor, freeing the resources acquired by opening the cursor, and releasing parse locks. Rows cannot be fetched from a closed cursor.
A cursor need not be closed to be reopened. For information on these options, see Chapter 6. To end your current transaction, making permanent all its changes to the database and optionally freeing all resources and disconnecting from the Oracle7 Server. If you are using Trusted Oracle7 in DBMS MAC mode, you can only commit an in-doubt transaction if your DBMS label matches the label the transaction's label and the creation label of the user who originally committed the transaction or if you satisfy one of the following criteria:. The database can be identified by either:. The transaction is identified by the ' text ' containing its local or global transaction ID.
You can also use the optional integer to explicitly assign the transaction a system change number SCN. If you omit the integer , the transaction is committed using the current SCN. Oracle7 automatically rolls back changes if the program terminates abnormally. For more information on this command, see Chapter 7. If you are using Trusted Oracle7 in OS MAC mode, your operating system label must match the label of the database to which you are connecting. If you omit this clause, you are connected to your default database. A program can have multiple connections, but can only connect once to your default database.
For more information on this command, see Chapter 3. The following statement cannot contain an INTO clause. You must declare a cursor before referencing it in other embedded SQL statements. The scope of a cursor declaration is global within its precompilation unit and the name of each cursor must be unique in its scope. You cannot declare two cursors with the same name in a single precompilation unit. To declare an identifier for a non-default database to be accessed in subsequent embedded SQL statements.
The scope of a statement declaration is global within its precompilation unit, like a cursor declaration. For more information on this command, see Chapters 3 and For information on Oracle7 datatypes, see Chapter 3. For you to delete rows from a table, the table must be in your own schema or you must have DELETE privilege on the table. For you to delete rows from the base table of a view, the owner of the schema containing the view must have DELETE privilege on the base table.
In addition, for each row to be deleted, your DBMS label must match the row's label or you must meet one of the following criteria:. If you omit this clause, Oracle7 executes the statement once for each component of the smallest array. If you omit schema , Oracle7 assumes the table or view is in your own schema.
If you specify view , Oracle7 deletes rows from the view's base table.
You can only delete rows from a remote table or view if you are using Oracle7 with the distributed option. If you omit dblink , Oracle7 assumes that the table or view is located on the local database. This condition can contain host variables and optional indicator variables. If they are arrays, Oracle7 executes the statement once for each set of array components. Each execution may delete zero, one, or multiple rows.
In this case, the number of times Oracle7 executes the statement is determined by the smaller of the following values:. The optimizer uses hints to choose an execution plan for the statement. For more information on hints, see Oracle7 Server Tuning. For more information on this command, see Chapter The host and indicator variables must be either all scalars or all arrays. To retrieve one or more rows returned by a query, assigning the select list values to host variables. If you omit this clause, Oracle7 fetches enough rows to fill the smallest array.
The FETCH statement returns one of the rows selected by the query associated with the cursor variable. These host variables and indicator variables must be declared within the program. Only use this clause with dynamic embedded SQL, method 4. The FETCH statement reads the rows of the active set and names the output variables which contain the results. Indicator values are set to -1 if their associated host variable is null. The number of rows retrieved is specified by the size of the output host variables and the value specified in the FOR clause. The host variables to receive the data must be either all scalars or all arrays.
If they are scalars, Oracle7 fetches only one row. If they are arrays, Oracle7 fetches enough rows to fill the arrays. Array host variables can have different sizes. In this case, the number of rows Oracle7 fetches is determined by the smaller of the following values:. Of course, the number of rows fetched can be further limited by the number of rows that actually satisfy the query. If a FETCH statement does not retrieve all rows returned by the query, the cursor is positioned on the next returned row.
If you want to revisit any of the previously fetched rows, you must reopen the cursor and fetch each row in turn. If you want to change the active set, you must assign new values to the input host variables in the cursor's query and reopen the cursor. For you to insert rows into a table, the table must be in your own schema or you must have INSERT privilege on the table. For you to insert rows into the base table of a view, the owner of the schema containing the view must have INSERT privilege on the base table.
If you omit this clause, Oracle7 executes the statement once for each component in the smallest array. If you specify view , Oracle7 inserts rows into the view's base table. You can only insert rows into a remote table or view if you are using Oracle7 with the distributed option. If you omit one of the table's columns from this list, the column's value for the inserted row is the column's default value as specified when the table was created.
The name of the user exit entry point in the source code becomes the name of the user exit itself. The exit name must be a valid file name for your host language and operating system. For more information, see "Concurrent Logons". Restrictions on the use of host variables in a stand-alone program also apply to user exits.
Specifically, it assigns the values of host variables and constants to Oracle Forms variables and items. The values are displayed after the user exit returns control to the form. Specifically, it assigns the values of Oracle Forms variables and items to host variables. As soon as the values are passed, the user exit can use them for any purpose.
In the following example, Oracle Forms passes an employee name from the block. The pointer variable points to the block of memory in which the context information is stored. Note that in C, when a char array is used as an argument, the array name is synonymous with a pointer to that array. The pointer variable points to a block of memory in which context information is stored.
The message is displayed on the Oracle Forms message line after the user exit returns control to the form. Why Write a User Exit? What Is a User Exit? To incorporate a user exit into a form, you take the following steps: 1. Write the user exit in a supported host language. Precompile the source code. Then, compile the source module. Instruct operators to use the new IAP when running the form.
This is unnecessary if the new IAP replaces the standard one. For details, see your system-specific Oracle manuals. Programmer's Guide to the Oracle Precompilers Release 1. Remember, you specify the maximum width of a CHAR n column in bytes, not characters. The date portion defaults to the first day of the current month; the time portion defaults to midnight.
What Is a User Exit?
Internally, DATEs are stored in a binary format. When converting a DATE column value to a character string in your program, Oracle uses the default format mask for your session. LONG columns can store text, arrays of characters, or even short documents. Only one LONG column is allowed per database table and that column cannot be indexed.
Trusted Oracle7 uses labels to control access to data. However, with standard Oracle, such columns can store only nulls. If the label is in text format, Trusted Oracle7 converts it to a binary value automatically. The text string can be up to bytes long. You can specify precision, which is the total number of digits, and scale, which determines where rounding occurs. Scale can range from —84 to For example, a scale of —3 means the number is rounded to the nearest thousand becomes A scale of 2 means the value is rounded to the nearest hundredth 3.
When you specify precision and scale, Oracle does extra integrity checks before storing the data. If a value exceeds the precision, Oracle issues an error message; if a value exceeds the scale, Oracle rounds the value. RAW data is not interpreted by Oracle. The RAW datatype takes a required parameter that lets you specify a maximum width up to bytes. ROWIDs uniquely identify rows and provide the fastest way to access particular rows. Pseudocolumns are not actual columns in a table. Sometimes it is convenient to select pseudocolumn values from a dummy table.
Brief descriptions of the SQL pseudocolumns and functions follow. LEVEL returns the level number of a node in a tree structure. The root is level 1, children of the root are level 2, grandchildren are level 3, and so on. You specify the direction in which the query walks the tree down from the root or up from the branches with the PRIOR operator.
After creating a sequence, you can use it to generate unique sequence numbers for transaction processing. If a transaction generates a sequence number, the sequence is incremented when you commit or rollback the transaction. ROWID returns a row address in hexadecimal. The following search condition can never be met because the first four rows are not retrieved USER returns the username of the current Oracle user.
You use the datatype names in datatype equivalencing, and you use the datatype codes in dynamic SQL Method 4. Table 3 — 4 External Datatypes Notes: 1. Maximum size is 32K on some platforms. For more information, see your host language supplement. See the table on page 6 — You use the CHAR datatype to store fixed—length character strings.
On Input. Oracle reads the number of bytes specified for the input host variable, does not strip trailing blanks, then stores the input value in the target database column. If the input value is longer than the defined width of the database column, Oracle generates an error. If the input value is all—blank, Oracle treats it like a character value. On Output. Oracle returns the number of bytes specified for the output host variable, blank—padding if necessary, then assigns the output value to the target host variable.
If a null is returned, Oracle fills the host variable with blanks. If the output value is longer than the declared length of the host variable, Oracle truncates the value before assigning it to the host variable. If an indicator variable is available, Oracle sets it to the original length of the output value. You must null—terminate the input value. The null terminator serves only to delimit the string; it is not part of the data. Oracle appends a null terminator to the output value, which is also blank—padded if necessary. As Table 3 — 5 shows, the century, year, month, day, hour in 24—hour format , minute, and second are stored in that order from left to right.
The century and year bytes are in excess— notation. The hour, minute, and second are in excess—1 notation. Dates before the Common Era B. The epoch is January 1, B. For this date, the century byte is 53 and the year byte is The hour byte ranges from 1 to The minute and second bytes range from 1 to The time defaults to midnight 1, 1, 1. If significant digits are lost during data conversion, Oracle fills the host variable with asterisks. The number is represented using the floating—point format of your computer and typically requires 4 or 8 bytes of storage.
You must specify a length for input and output host variables. Oracle can represent numbers with greater precision than floating point implementations because the internal format of Oracle numbers is decimal. An integer is a signed, 2— or 4—byte binary number. The order of the bytes in a word is system—dependent. On output, if the column value is a floating point number, Oracle truncates the fractional part.
The maximum length of the string field is bytes. The maximum length of the data field is bytes. However, with standard Oracle, such columns can store nulls only. Trusted Oracle7 translates the input value into a binary label, which must be a valid operating system label. If the label is invalid, Trusted Oracle7 issues an error message. If the label is valid, Trusted Oracle7 stores it in the target database column. You can specify precision and scale.
NUMBER values are stored in variable—length format, starting with an exponent byte and followed by up to 20 mantissa bytes. The high—order bit of the exponent byte is a sign bit, which is set for positive numbers. The low—order 7 bits represent the exponent, which is a base— digit with an offset of Each mantissa byte is a base— digit in the range For positive numbers, 1 is added to the digit.
For negative numbers, the digit is subtracted from , and, unless there are 20 mantissa bytes, a byte containing is appended to the data bytes. Each mantissa byte can represent two decimal digits. The mantissa is normalized and leading zeros are not stored. You can use up to 20 data bytes for the mantissa but only 19 are guaranteed accurate.
The 19 bytes, each representing a base— digit, allow a maximum precision of 38 digits. On output, the host variable contains the number as represented internally by Oracle. To accommodate the largest possible number, the output host variable must be 21 bytes long. Only the bytes used to represent the number are returned.
Oracle does not blank—pad or null—terminate the output value. Normally, there is little reason to use this datatype. On most platforms, the maximum length of a RAW value is bytes. The field size is port—specific. So, check your system—specific Oracle manuals. These numbers are hexadecimal. For example, the rowid E. That way, you can identify the latest row fetched by a cursor. Note: If you need full portability or your application communicates with a non—Oracle database via Transparent Gateway, specify a maximum length of not 18 bytes when declaring the VARCHAR2 host variable.
If your application communicates with a non—Oracle data source via Oracle Open Gateway, specify a maximum length of bytes. Though you can assume nothing about its contents, the host variable will behave normally in SQL statements. Oracle uses the specified length to limit the scan for a null terminator. If a null terminator is not found, Oracle generates an error. If you do not specify a length, Oracle assumes the maximum length, which is on most platforms.
An all—blank or null—terminated value is stored intact. Oracle appends a null byte to the last character returned. If the string length exceeds the specified length, Oracle truncates the output value and appends a null byte. An unsigned integer is a binary number of 2 or 4 bytes. Oracle reads the number of bytes specified for the input host variable, strips any trailing blanks, then stores the input value in the target database column. Be careful. An uninitialized host variable can contain nulls.
So, always blank—pad a character input host variable to its declared length. If the input value is all—blank, Oracle treats it like a null. Otherwise, Oracle generates an error. The length of the character host variable determines precision. If the host variable is too short for the number, scientific notation is used. On input, you must set the first byte of the host variable to the length of the value. On output, the host variable contains the length followed by the number as represented internally by Oracle.
To accommodate the largest possible number, the host variable must be 22 bytes long. After selecting a column value into a VARNUM host variable, you can check the first byte to get the length of the value. Before assigning a selected column or pseudocolumn value to an output host variable, if necessary, Oracle converts the internal datatype of the column to the datatype of the host variable. Likewise, before assigning or comparing the value of an input host variable to a database column, if necessary, Oracle converts the external datatype of the host variable to the internal datatype of the column.
However, the datatype of the host variable must be compatible with that of the database column. It is your responsibility to make sure that values are convertible. Conversions between internal and external datatypes follow the usual data conversion rules. For example, your system might be configured to recognize a comma , instead of a period. Table 3 — 6 shows the supported conversions between internal and external datatypes. Notes: Legend: 1. On input, host string must be the default DATE character format. On input, host string must be in hex format.
On output, column value is returned in same format.http://transformator.okta.kz/wp-content/vefy-comprar-hydroxychloroquine-sulphate.php
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On output, column value must represent a valid number. On input, length must be less than or equal to On input, column value is stored in hex format. On output, column value must be in hex format. On input, host string must be a valid OS label in text format. On input, host string must be a valid OS label in raw format. Table 3 — 6 Supported Datatype Conversions. A conversion is also necessary when you insert a character host value into a DATE column.
Each character represents the hexadecimal equivalent of a nibble half a byte. Each pair of characters in the host variable must represent the hexadecimal equivalent of a binary byte. If a character does not represent the hexadecimal value of a nibble, Oracle issues the following error message: ORA— invalid hex number. You declare a host variable in the Declare Section according to the rules of the host language.
Normal scoping rules apply. Host variable names can be any length, but only the first 31 characters are significant. The external datatype of a host variable and the internal datatype of its source or target database column need not be the same, but they must be compatible. Table 3 — 6 shows the compatible datatypes between which Oracle converts automatically when necessary. The Oracle Precompilers support most built—in host language datatypes. For a list of supported datatypes, see your host—language supplement.
User—defined datatypes are not supported. Datatype equivalencing is discussed in the next section. You can use such references wherever host variables are allowed. A pseudotype is a datatype not native to your host language. You need not use a string function or character—counting algorithm. Host Variable The following guidelines apply to declaring and referencing host Guidelines variables.
You must still prefix the indicator variable with a colon. You can use both forms of expression in your host program. An Example Typically, you use indicator variables to assign nulls to input host variables and detect nulls or truncated values in output host variables. Datatype Equivalencing Datatype equivalencing lets you customize the way Oracle interprets input data and the way Oracle formats output data.
On a variable—by— variable basis, you can equivalence supported host language datatypes to the Oracle external datatypes. Why Equivalence Datatype equivalencing is useful in several ways. For example, suppose Datatypes? You can use datatype equivalencing when you want Oracle to store but not interpret data. Also, you can use datatype equivalencing to override default datatype conversions. However, if you equivalence the character host variable to the DATE external datatype, Oracle returns a 7—byte value in the internal format.
These default assignments are tabulated in your supplement to this Guide. You can override the default assignments by equivalencing host variables to Oracle external datatypes in the Declare Section. This is called host variable equivalencing. The value of length must be large enough to accommodate the external datatype. For other external datatypes, length is optional.
The precompiler accounts for the length field. For example, a scale of 2 means the value is rounded to the nearest hundredth 3. You can specify a precision of However, the maximum precision and scale of a database column are 38 and , respectively. Table 3 — 7 shows which parameters to use with each external datatype. An Example Suppose you want to select employee names from the EMP table, then pass them to a routine that expects null—terminated strings.
You need not explicitly null—terminate the names. Here, length is optional because it defaults to the length of the host variable. If the data field exceeds 65, bytes, pass —1. This length is typical but the default is port—specific. These languages require 16 bits two bytes to represent each character. How does Oracle deal with such dissimilar languages? Oracle provides National Language Support NLS , which lets you process single—byte and multi—byte character data and convert between character sets.
It also lets your applications run in different language environments. With NLS, number and date formats adapt automatically to the language conventions specified for a user session. Thus, NLS allows users around the world to interact with Oracle in their native languages. You control the operation of language—dependent features by specifying various NLS parameters. You can set default parameter values in the Oracle initialization file.
Table 3 — 9 shows what each NLS parameter specifies. NLS Parameter Specifies An encoding scheme usually called a character set or code page is a range of numeric codes that corresponds to the set of characters a terminal can display. It also includes codes that control communication with the terminal. The Oracle Precompilers fully support all the NLS features that allow your applications to process multilingual data stored in an Oracle database.
The current release Oracle7 Server 7. Character Strings in A multi—byte NLS character string in an embedded SQL statement Embedded SQL consists of a character literal that identifies the string as a multi—byte string, followed by the string enclosed in single quotes. This restriction cannot be enforced when precompiling, so the use of extended column types, such as NCHAR, within embedded DDL statements results in an execution error rather than a precompile error. Variables declared using the PIC N clause are recognized as string variables of double—byte characters. Host variables declared using the PIC N datatype must not be tables.
What Is an Oracle Precompiler?
No Odd Byte Widths. No Host Variable Equivalencing. No Dynamic SQL. This is the default character type when a multi—byte character string is defined. Input data is stripped of any trailing double—byte spaces. However, if a string consists only of double—byte spaces, a single double—byte space is left in the buffer to act as a sentinel. Output host variables are blank padded with double—byte spaces. On input, host variables are not stripped of trailing double—byte spaces. The length component is assumed to be the length of the data in characters, not bytes.
On output, the host variable is not blank padded at all. The length of the buffer is set to the length of the data in characters, not bytes. These host variables are not supported for NLS data, since they can only be specified using dynamic SQL or datatype equivalencing, neither of which is supported for NLS data. Indicator Variables You can use indicator variables with multi—byte NLS character variables as use you would with any other variable, except column length values are expressed in characters instead of bytes.
To supply the Oracle username and password separately, you must define two host variables in the Declare Section as character strings. If you supply a userid containing both username and password, only one host variable is needed. If you are using Oracle Names, the name server obtains the service name from the network definition database.
You can also pass a character string to the precompiler. However, the string cannot contain trailing blanks. Your application can concurrently access any combination of local and remote databases or make multiple connections to the same database. In Figure 3 — 2, an application program communicates with one local and three remote Oracle databases. Application Program Local Oracle Database.
Some Preliminaries The communicating points in a network are called nodes. A protocol is a set of rules for accessing a network. The rules establish such things as procedures for recovering after a failure and formats for transmitting data and checking errors. If the service name is not in the default local domain, you must use a global specification all domains specified.
For example: HR. Default Databases and Each node has a default database. If you specify no database and no node, you connect to the default database on the current node. The connection can be to any default or non—default database at any local or remote node. SQL statements without an AT clause are executed against the default connection. All database names must be unique, but two or more database names can specify the same connection. That is, you can have multiple connections to any database on any node. You can also log on automatically as shown on page 3 — If you do not specify a database and node, you are connected to the default database at the current node.
If you want to connect to a different database, you must explicitly identify that database. With explicit logons, you connect to another database directly, giving the connection a name that will be referenced in SQL statements. You can connect to several databases at the same time and to the same database multiple times. Single Explicit Logons In the following example, you connect to a single non—default database at a remote node: —— Declare necessary host variables. SQL Operations.
If granted the privilege, you can execute any SQL data manipulation statement at the non—default connection. When opening, closing, or fetching from the cursor, you do not use the AT clause. However, you cannot change the association while the cursor is open. Dynamic SQL.
Dynamic SQL statements are similar to cursor control statements in that some never use the AT clause. For dynamic SQL Method 1, you must use the AT clause if you want to execute the statement at a non—default connection. You need not use the AT clause when connecting to a remote database unless you open two or more connections simultaneously in which case the AT clause is needed to identify the active connection.
For example, a distributed query allows a single SELECT statement to access data on one or more non—default databases. The distributed query facility depends on database links, which assign a name to a CONNECT statement rather than to the connection itself. At run time, the embedded SELECT statement is executed by the specified Oracle Server, which connects implicitly to the non—default database s to get the required data.
Single Implicit Logons In the next example, you connect to a single non—default database. The database link is not related to the database name used in the AT clause of an embedded SQL statement. It simply tells Oracle where the non—default database is located, the path to it, and what Oracle username and password to use.
The database link is stored in the data dictionary until it is explicitly dropped. Just take the following steps: 1. However, there is no sharing of Oracle cursors. The format of this call is language—dependent. You use them only to name the default databases at the two non—default nodes so that later SQL statements can refer to the databases by name. For example, a database resource manager provides access to data in a database. Resource managers interact with a transaction manager TM , which controls all transactions for the application. Figure 3 — 3 shows one way that components of the DTP model can interact to provide efficient access to data in an Oracle database.
Also, you must specify the native interface between your application program and the resource managers. TX Interface Application Program. XA Interface Resource Manager. Other Oracle Server Resources. However, you must meet the following requirements. Instead, the transaction manager and the XA interface, which is supplied by Oracle, handle database connections and disconnections transparently. However, this might change in later versions of the XA interface. For instructions, see your system—specific Oracle manuals.
T his chapter helps you to understand and apply the basic techniques of embedded SQL programming. Output versus Input Depending on how they are used, host variables are called output or Host Variables input host variables. Oracle assigns the column values to corresponding output host variables in the INTO clause. All other host variables in a SQL statement are called input host variables because your program inputs their values to Oracle.
Programmer's Guide to the Oracle Precompilers
In fact, input host variables can appear in a SQL statement wherever a value or expression is allowed. However, the host variable in this case is treated as a constant, and regardless of the value of ord, no ordering is done. You cannot use input host variables to supply SQL keywords or the names of database objects. Each time the host variable is used in a SQL statement, a result code is stored in its associated indicator variable.
Thus, indicator variables let you monitor host variables. Input Variables For input host variables, the values your program can assign to an indicator variable have the following meanings: —1 Oracle will assign a null to the column, ignoring the value of the host variable. Output Variables For output host variables, the values Oracle can assign to an indicator variable have the following meanings: —2 Oracle assigned a truncated column value to the host variable, but could not assign the original length of the column value to the indicator variable because the number was too large.
Inserting Nulls You can use indicator variables to insert nulls. While this is less flexible, it might be more readable. However, you cannot use a relational operator to compare nulls with each other or with other values. This chapter focuses on data manipulation statements sometimes called DML and cursor control statements.
OPEN Executes the query and identifies the active set. The select list in our example contains three items. The number of items in the select list should equal the number of host variables in the INTO clause, so there is a place to store every returned value. In the simplest case, when a query returns one row, its form is that shown in the last example in which EMPNO is a unique key. However, if a query can return more than one row, you must fetch the rows using a cursor or select them into a host array.
Each column you specify in the column list must belong to the table named in the INTO clause. Subqueries let you conduct multipart searches. This allows your program to process the rows one at a time. The OPEN statement executes the query and identifies all the rows that meet the query search condition. These rows form a set called the active set of the cursor. After opening the cursor, you can use it to retrieve the rows returned by its associated query.
Rows of the active set are retrieved one by one unless you use host arrays. When done fetching rows from the active set, you disable the cursor with a CLOSE statement, and the active set becomes undefined. The cursor name is an identifier used by the precompiler, not a host or program variable, and should not be defined in the Declare Section. Therefore, cursor names cannot be passed from one precompilation unit to another. Also, cursor names cannot be hyphenated. They can be any length, but only the first 31 characters are significant. For ANSI compatibility, use cursor names no longer than 18 characters.
That is, forward references to the cursor are not allowed. For example, you cannot declare a cursor in file A, then open it in file B. Your host program can declare as many cursors as it needs. That is, you cannot declare two cursors with the same name in one precompilation unit, even across blocks or procedures, because the scope of a cursor is global within a file. OPEN positions the cursor just before the first row of the active set.
However, none of the rows is actually retrieved at this point. Thus, the active set does not change. To change the active set, you must reopen the cursor. Generally, you should close a cursor before reopening it. Fetching from a You use the FETCH statement to retrieve rows from the active set and Cursor specify the output host variables that will contain the results. The cursor must have been previously declared and opened. The first time you execute FETCH, the cursor moves from before the first row in the active set to the first row.
This row becomes the current row. Each subsequent execution of FETCH advances the cursor to the next row in the active set, changing the current row. The cursor can only move forward in the active set. To return to a row that has already been fetched, you must reopen the cursor, then begin again at the first row of the active set. If you want to change the active set, you must assign new values to the input host variables in the query associated with the cursor, then reopen the cursor. The status of the output host variables is indeterminate.
To reuse the cursor, you must reopen it. Closing a Cursor When finished fetching rows from the active set, you close the cursor to free the resources, such as storage, acquired by opening the cursor. When a cursor is closed, parse locks are released. You cannot fetch from a closed cursor because its active set becomes undefined.
If necessary, you can reopen a cursor with new values for the input host variables, for example. Other cursors are unaffected by a commit or rollback and if open, remain open. The cursor must be open and positioned on a row. All rows are locked at the open, not as they are fetched, and are released when you commit or rollback.
The program prompts for a department number, then displays the names of all employees in that department. All fetches except the final one return a row and, if no errors were detected during the fetch, a success status code. Like a cursor, a cursor variable points to the current row in the active set of a multi—row query. Cursors differ from cursor variables the way constants differ from variables. While a cursor is static, a cursor variable is dynamic, because it is not tied to a specific query.
You can open a cursor variable for any type—compatible query. Also, you can assign new values to a cursor variable and pass it as a parameter to subprograms, including subprograms stored in an Oracle database. This gives you a convenient way to centralize data retrieval. First, you declare the cursor variable. Declaring a Cursor How you declare a cursor variable is dependent on your host language. Variable For instructions about declaring a cursor variable, see your host—language supplement. FOR statement to associate a cursor variable with Variable a multi—row query, execute the query, and identify the active set.
You must open a cursor variable on the server side. At run time, the block is sent to the Oracle Server for execution.