mysql - 在 mysql8 中，为什么 DATE DEFAULT CURRENT_DATE 需要在 CURRENT_DATE 周围加括号？

Question

从 mysql8 开始，这是合法的:

CREATE TABLE t (d DATETIME DEFAULT CURRENT_TIMESTAMP);

这是合法的:

CREATE TABLE t (d DATE DEFAULT (CURRENT_DATE));

那么为什么这是非法的？

CREATE TABLE t (d DATE DEFAULT CURRENT_DATE);

导致

Error in query (1064): Syntax error near 'CURRENT_DATE)' at line 1

Answer 1

引用this for more information .

这很可能是您在问题中所指的内容:

The default value specified in a DEFAULT clause can be a literal constant or an expression. With one exception, enclose expression default values within parentheses to distinguish them from literal constant default values.

[...]

The exception is that, for TIMESTAMP and DATETIME columns, you can specify the CURRENT_TIMESTAMP function as the default, without enclosing parentheses.