本文介绍了如果(从表中选择计数(列))>0 那么的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我需要检查一个条件.即:
I need to check a condition. i.e:
if (condition)> 0 then update table else do not update end if是否需要使用 select into 将结果存储到变量中?
Do I need to store the result into a variable using select into?
例如:
declare valucount integer begin select count(column) into valuecount from table end if valuecount > o then update table else do not update 推荐答案不能在 PL/SQL 表达式中直接使用 SQL 语句:
You cannot directly use a SQL statement in a PL/SQL expression:
SQL> begin 2 if (select count(*) from dual) >= 1 then 3 null; 4 end if; 5 end; 6 / if (select count(*) from dual) >= 1 then * ERROR at line 2: ORA-06550: line 2, column 6: PLS-00103: Encountered the symbol "SELECT" when expecting one of the following: ... ...您必须改用变量:
SQL> set serveroutput on SQL> SQL> declare 2 v_count number; 3 begin 4 select count(*) into v_count from dual; 5 6 if v_count >= 1 then 7 dbms_output.put_line('Pass'); 8 end if; 9 end; 10 / Pass PL/SQL procedure successfully completed.当然,您可以在 SQL 中完成整个操作:
Of course, you may be able to do the whole thing in SQL:
update my_table set x = y where (select count(*) from other_table) >= 1;很难证明某些事情是不可能的.除了上面的简单测试用例,您可以查看 IF 语句的语法图;您不会在任何分支中看到 SELECT 语句.
It's difficult to prove that something is not possible. Other than the simple test case above, you can look at the syntax diagram for the IF statement; you won't see a SELECT statement in any of the branches.
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如果(从表中选择计数(列))>0 那么
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