CREATE OR REPLACE FUNCTION "public"."nvl"("p_value1" varchar, "p_value2" varchar) RETURNS "pg_catalog"."varchar" AS $BODY$ BEGIN IF P_VALUE1 IS NULL OR P_VALUE1 = '' THEN RETURN P_VALUE2; ELSE RETURN P_VALUE1; END IF; END; $BODY$ LANGUAGE plpgsql VOLATILE COST 100
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nccloud
COALESCE函数
COALESCE函数是返回参数中的第一个非null的值，它要求参数中至少有一个是非null的;
selectcoalesce(1,null,2),coalesce(null,'2',1),coalesce(null,null,null);
NULLIF(ex1,ex2)函数如果ex1与ex2相等则返回Null，不相等返回第一个表达式的值;
selectnullif(1,2),nullif(2,null),nullif(2,2);
NVL函数是将NULL值的字段转换成默认字段输出;这个是oracle中的函数，不过可以在pg数据库中创建函数来达到该目的;
--/
CREATE OR REPLACE FUNCTION "public"."nvl"("p_value1" varchar, "p_value2" varchar)
RETURNS "pg_catalog"."varchar" AS $BODY$
BEGIN
IF P_VALUE1 IS NULL OR P_VALUE1 = '' THEN
RETURN P_VALUE2;
ELSE
RETURN P_VALUE1;
END IF;
END;
$BODY$
LANGUAGE plpgsql VOLATILE
COST 100
/