operator precedence in mysql

Question

哪个运算符： /或*在MySQL具有更高的优先级？

Answer 1

Like most programming languages, mysql performs / and * (as well as DIV, % and MOD) from left to right, in the order they occur. For instance:

1 / 2 * 3 / 4 / 5 * 6

is equivalent to

((((1 / 2) * 3) / 4) / 5) * 6

See http://dev.mysql.com/doc/refman/5.0/en/operator-precedence.html for a complete list of operator precedence.

Answer 2

The operators are prioritized as listed from the highest precedence to the lowest:

1. BINARY, COLLATE
2. NOT (logical negation), ! (logical negation)
3. .- (unary minus), ~ (unary bit inversion)
4. ^ (bitwise exclusive OR comparison)
5. .* (multiplication), / (division), % (modulo)
6. .- (subtraction), + (addition)
7. << (bitwise shift left), >> (bitwise shift right)
8. & (bitwise AND)
9. | (bitwise OR)
10. Comparison operators such as < >
11. BETWEEN, NOT BETWEEN
12. AND && (conjuction - logical addition)
13. XOR (logical exclusive OR comparison)
14. OR || (disjunction - either/or comparison)

As per list, the comparison BINARY operator has precedence over the BETWEEN and ampersand (&) operators. Operators on the same line above have the same level of precedence, and are evaluated in the order of usage.

Source http://www.learn-mysql-tutorial.com/Expressions.cfm

Answer 3

它们是相同的，请参见http://dev.mysql.com/doc/refman/5.0/en/operator-precedence.html

Answer 4

They have the same precedence, * is listed first, and MySQL will evaluate left to right.

http://dev.mysql.com/doc/refman/5.0/en/operator-precedence.html

My advice is use brackets () to make things clear.

It's always best to check, and that can be done very easily with MySQL:

mysql> SELECT 2*3/2, 2/3*2, 2*(3/2) ;
+--------+--------+---------+
| 2*3/2  | 2/3*2  | 2*(3/2) |
+--------+--------+---------+
| 3.0000 | 1.3333 |  3.0000 | 
+--------+--------+---------+
1 row in set (0.00 sec)

Answer 5

/ or * will have the highest priority in mysql.

They're of same priority.

Answer 6

The answer is: it shouldn't matter. If you have an expression that you are not sure how it's evaluated, use parens. They're free.