MySQL中IF语句的正确语法是什么？ [英] What is the right syntax of IF statement in MySQL?

问题描述

我有一个小而简单的MySQL代码。但每当我运行它时，我都会收到错误＃1064。你能告诉我这里的错误是什么吗？

I have a small and simple MySQL code. But whenever I run it, I get error #1064. Can you tell me what is my mistake here?

IF ((SELECT COUNT(id) FROM tbl_states) > 0) THEN
    BEGIN
        SELECT * FROM tbl_cities;
    END
END IF

我还使用了一些其他条件如下，但我又得到了一个错误。

I also used some other conditions like the below one, but again I got an error.

IF (1=1) THEN
    BEGIN
        SELECT * FROM tbl_cities;
    END
END IF

我真正想做的是这样的事情：

What I actually want to do is something like this:

IF ((SELECT COUNT(id) FROM tbl_states) > 0) THEN
    BEGIN
        UPDATE ...
    END
ELSE
    BEGIN
        INSERT ...
    END
END IF

推荐答案

如果是您正在编写的程序，请尝试：

If it is a procedure you're writing you should try:

BEGIN
    IF ((SELECT COUNT(id) FROM tbl_states) > 0) THEN
        SELECT * FROM tbl_cities;
    END IF
END

如果是查询， BEGIN 和 END 此处无关。

If it is a query, BEGIN and END have nothing to do here.

编辑

好吧，没有更多要说的， IF（（SELECT COUNT（id）FROM tbl_states）> 0）那么SELECT * FROM tbl_cities; END IF 根本不尊重基本的MySQL SELECT语句 。

Well, there is not really more to say, IF ((SELECT COUNT(id) FROM tbl_states) > 0) THEN SELECT * FROM tbl_cities; END IF is simply not respecting the basic MySQL SELECT statement.

你应该从 SELECT ......等开始......

You should start with SELECT... etc...

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