14.4.1 运算符优先级
Operator precedences are shown in the following list, from highest precedence to the lowest. Operators that are shown together on a line have the same precedence.
INTERVAL
BINARY, COLLATE
!
- (unary minus), ~ (unary bit inversion)
^
*, /, DIV, %, MOD
-, +
<<, >>
&
|
= (comparison), <=>, >=, >, <=, <, <>, !=, IS, LIKE, REGEXP, IN, MEMBER OF
BETWEEN, CASE, WHEN, THEN, ELSE
NOT
AND, &&
XOR
OR, ||
= (assignment), :=
The precedence of =
depends on whether it is used as a comparison operator (=
) or as an assignment operator (=
). When used as a comparison operator, it has the same precedence as <=>
, >=
, >
, <=
, <
, <>
, !=
, IS
, LIKE
, REGEXP
, and IN()
. When used as an assignment operator, it has the same precedence as :=
. Section 15.7.6.1, “SET Syntax for Variable Assignment”, and Section 11.4, “User-Defined Variables”, explain how MySQL determines which interpretation of =
should apply.
For operators that occur at the same precedence level within an expression, evaluation proceeds left to right, with the exception that assignments evaluate right to left.
The precedence and meaning of some operators depends on the SQL mode:
-
By default,
||
is a logicalOR
operator. WithPIPES_AS_CONCAT
enabled,||
is string concatenation, with a precedence between^
and the unary operators. -
By default,
!
has a higher precedence thanNOT
. WithHIGH_NOT_PRECEDENCE
enabled,!
andNOT
have the same precedence.
See Section 7.1.11, “Server SQL Modes”.
The precedence of operators determines the order of evaluation of terms in an expression. To override this order and group terms explicitly, use parentheses. For example:
mysql> SELECT 1+2*3;
-> 7
mysql> SELECT (1+2)*3;
-> 9