if operator

数据库 myql sql_statement

• IF(expr1,expr2,expr3)

If expr1 is TRUE (expr1 <> 0 and expr1 <> NULL), IF() returns expr2. Otherwise, it returns expr3.
如果表达式 1是真 真则返回表达式2 ，否则返回表达式3（假）

The default return type of IF() (which may matter when it is stored into a temporary table) is calculated as follows:
IF（）的默认返回类型（将其存储到临时表中时可能很重要）的计算如下：

• If expr2 or expr3 produce a string, the result is a string.
  If expr2 and expr3 are both strings, the result is case-sensitive if either string is case-sensitive. 如果两者都是字符创 ，而其中任意字符创区分大小写，则结果也是区分大小写
• If expr2 or expr3 produce a floating-point value, the result is a floating-point value.
  如果expr2或expr3产生浮点值 则结果也是浮点值
• If expr2 or expr3 produce an integer, the result is an integer.