tailieunhanh - PL/SQL User's Guide and Reference 10g Release phần 8

Tham khảo tài liệu 'pl/sql user's guide and reference 10g release phần 8', công nghệ thông tin, cơ sở dữ liệu phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Cursors TYPE Provides the datatype of a previously declared user-defined record. Usage Notes You must declare a cursor before referencing it in an OPEN FETCH or CLOSE statement. You must declare a variable before referencing it in a cursor declaration. The word SQL is reserved by PL SQL as the default name for implicit cursors and cannot be used in a cursor declaration. You cannot assign values to a cursor name or use it in an expression. However cursors and variables follow the same scoping rules. For more information see Scope and Visibility of PL SQL Identifiers on page 2-14. You retrieve data from a cursor by opening it then fetching from it. Because the FETCH statement specifies the target variables using an INTO clause in the SELECT statement of a cursor_declaration is redundant and invalid. The scope of cursor parameters is local to the cursor meaning that they can be referenced only within the query used in the cursor declaration. The values of cursor parameters are used by the associated query when the cursor is opened. The query can also reference other PL SQL variables within its scope. The datatype of a cursor parameter must be specified without constraints that is without precision and scale for numbers and without length for strings. Examples Some examples of cursor declarations follow CURSOR cl IS SELECT empno ename job sal FROM emp WHERE sal 2000 CURSOR c2 RETURN dept ROWTYPE IS SELECT FROM dept WHERE deptno l0 CURSOR c3 start_date DATE IS SELECT empno sal FROM emp WHERE hiredate start_date Related Topics CLOSE Statement FETCH Statement OPEN Statement SELECT INTO Statement 13-40 PL SQL User s Guide and Reference DELETE Statement DELETE Statement The DELETE statement removes entire rows of data from a specified table or view. For a full description of the DELETE statement see Oracle Database SQL Reference. Syntax delete_statement table reference ------------ - subquerỵ Ợ --------------- TABLE - subquerỵ2 table_reference Keyword and Parameter .

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