Cursors in PL/SQL

Every SQL statement executed by the RDBMS has a private SQL area that contains information about the SQL statement and the set of data returned. In PL/SQL, a cursor is a name assigned to a specific private SQL area for a specific SQL statement. There can be either static cursors, whose SQL statement is determined at compile time, or dynamic cursors, whose SQL statement is determined at runtime. Static cursors are used only for DML statements (SELECT, INSERT, UPDATE, DELETE, MERGE, or SELECT FOR UPDATE). These static cursors can be explicitly declared and named or may appear in-line as an implicit cursor. Dynamic cursors are used for any type of valid SQL statement including DDL (CREATE, TRUNCATE, ALTER) and DCL (GRANT, REVOKE). Dynamic cursors are implemented with the EXECUTE IMMEDIATE statement.

Explicit Cursors

Explicit cursors are SELECT statements that are DECLAREd explicitly in the declaration section of the current block or in a package specification. Use OPEN, FETCH, and CLOSE in the execution or exception sections of your programs.

Declaring explicit cursors

To use an explicit cursor, you must first declare it in the declaration section of a block or package. There are three types of explicit cursor declarations:

  • A cursor without parameters; for example:

    CURSOR company_cur 
       SELECT company_id FROM company;
  • A cursor that accepts arguments through a parameter list; for example:

    CURSOR company_cur (id_in IN NUMBER) IS SELECT name FROM company WHERE company_id ...

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