[英]Dynamically pass table name to a query db2
I need to do COUNT from table, which name is build dynamically and store the value 我需要从表中执行COUNT,该表是动态生成的并存储值
Tried two approaches, unsuccessful: 尝试了两种方法,但均未成功:
SET COUNT = (SELECT COUNT(*) FROM BUILD_FUNCTION_NAME(a,b))
SET NAME = BUILD_FUNCTION_NAME(a,b)
SET COUNT = ( SELECT COUNT(*) FROM NAME)
If it's DB2 for LUW, then try this: 如果是DB2 for LUW,请尝试以下操作:
--#SET TERMINATOR @
CREATE OR REPLACE FUNCTION GET_COUNT(P_TABNAME VARCHAR(256))
RETURNS BIGINT
BEGIN
DECLARE V_RC BIGINT;
PREPARE S1 FROM 'SET ? = (SELECT COUNT(1) FROM '||P_TABNAME||')';
EXECUTE S1 INTO V_RC;
RETURN V_RC;
END@
VALUES GET_COUNT('SYSCAT.TABLES')@
VALUES GET_COUNT('SYSCAT.COLUMNS')@
VALUES GET_COUNT('(SELECT 1 FROM SYSCAT.TABLES WHERE TABSCHEMA LIKE ''SYS%'')')@
You can pass even an arbitrary SELECT
statement into such a function as a parameter. 您甚至可以将任意
SELECT
语句作为参数传递给函数。
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