MySQL-commonly used functions
1. Mathematical functions
| Function name | Features |
|---|---|
| ABS(x) | Returns the absolute value of x |
| SQRT(x) | Returns the square root of a non-negative number x |
| CEIL(x),CEILIN(x) | Returns the smallest integer value not less than x |
| FLOOR(x) | Returns the largest integer value not greater than x |
| RAND() | Return a random number from 0 to 1 |
| RAND(x) | Return a random number from 0 to 1, the same random number will be returned when the x value is the same |
| SIGN(x) | The return parameter is the sign of -1, 0, 1, and the sign depends on the value of x being negative, zero or positive |
| PI() | Returns the PI, the default display decimal place is 7 digits, mysql will use the full double-precision value internally |
| TRUNCATE(x,y) | Return the value x to the y place value after the decimal point |
| ROUND(x) | Returns the integer closest to x |
| ROUND(x,y) | Keep the value of y digits after the x decimal point, but round off when truncating |
| POW (x, y), POWER (x, y) | Returns the result of x to the y power |
| EXP(x) | Returns the value of e (the base of the natural logarithm) raised to the x power |
| MOD (x, y) | Returns the remainder after dividing x by y |
| LOG(x) | Returns the base 2 logarithm of x |
| LOG10(x) | Returns the base 10 logarithm of x |
| RADIANS(x) | Convert angle to radians |
| DEGREES(x) | Convert radians to angles |
| SIN (x) | Returns the sine of x, where x is given in radians |
| ASIN(x) | Returns the arc sine of x, that is, the sine is the value of x. If x is not in -1~1, return null |
| COS(x) | Returns the cosine of x, where x is given in radians |
| ACOS(x) | Returns the arc cosine of x, which is the value of x. If x is not in -1~1, return null |
| SO (x) | Returns the arctangent value, that is, the value where the tangent is x |
| ATAN (x), ATAN (x, y) | Returns the arc tangent of two variables x and y. |
| COT(x) | Returns the cotangent of x |
| SIGN() | Return the sign of the current result, if it is a negative number, return -1, if it is 0, return 0, if it is a positive number, return 1 |
| FORMAT(x,y) | Thousands will be automatically |
fromat
[Note: Once your data is separated by thousands, it will become a string. The calculation will be very troublesome afterwards, so it is not recommended to use]
Two, string functions
Three, date function
Four, system information function
| Function name | Features |
|---|---|
| BENCHMARK(count,expr) | Run the expression expr count times |
| CONNECTION_ID() | Returns the connection ID of the current client |
| FOUND_ROWS() | Returns the total number of rows retrieved by the last SELECT query |
| USER()或SYSTEM_USER() | Return the current login user name |
| VERSION() | Returns the version of the MySQL server |
Five, statistical functions
count(): generally use count(1) instead of count(*), you can also put fields