"MySQL function" MySQL 5.5 starting from scratch sixth chapter

Description: This article summarizes from: "MySQL 5.5 Start from scratch" chapter sixth

The functions in MySQL include:

Mathematical functions, String functions, date and time functions, conditional judgment functions, System information functions and cryptographic functions.

Function:

Represents a value that returns a specific relationship to the input parameter value.

First, mathematical functions

The main mathematical functions are: absolute value function, trigonometric function (including sine function, cosine function, tangent function, cotangent function, etc.),

Logarithmic functions, random functions, and so on. (PS: The math function will return NULL if there is an error)

1.1 Absolute Value function abs (x)

Mysql> SELECT ABS (1), ABS ( -1.1), ABS ( -33), +--------+-----------+----------+| ABS (1) | ABS (-1.1) | ABS ( -33) |+--------+-----------+----------+|      1 |       1.1 |       |+--------+-----------+----------+1 row in Set (0.03 sec)

1.2 Returning pi function pi ()

Mysql> SELECT PI (); +----------+| PI ()     3.141593 |+----------+1 row in Set (0.00 sec)

1.3 Square root function sqrt (x)

　PS:SQRT (x) range two root of nonnegative x

Mysql> SELECT SQRT (9), SQRT (Ten), SQRT ( -9), +---------+--------------------+----------+| SQRT (9) | SQRT (Ten)           | SQRT ( -9) |+---------+--------------------+----------+|       3 | 3.1622776601683795 |     NULL |--negative number without square root +---------+--------------------+----------+1 row in Set (0.00 sec)

1.4 Complementary function mod (x, y)

Mysql> Select mod (5,2), mod (7,4), mod (50,8), +----------+----------+-----------+| MOD (5,2) | MOD (7,4) | MOD (50,8) |+----------+----------+-----------+|        1 |        3 |         2 |+----------+----------+-----------+1 row in Set (0.00 sec)

1.5 functions to get integers ceil (x), CEILING (x), floor (x)

　Ps:ceil (x), CEILING (x) have the same meaning

Mysql> SELECT ceil ( -2.26), ceil (2.26), CEILING ( -2.26), CEILING (2.26), +-------------+------------+--------------- -+---------------+| Ceil (-2.26) | Ceil (2.26) | CEILING (-2.26) | CEILING (2.26) |+-------------+------------+----------------+---------------+|          -2 |          3 |             -2 |             3 |+-------------+------------+----------------+---------------+1 row in Set (0.00 sec)

Mysql> SELECT Floor ( -2.26), floor (2.26), +--------------+-------------+| Floor (-2.26) | Floor (2.26) |+--------------+-------------+|           -3 |           2 |+--------------+-------------+1 row in Set (0.00 sec)

1.6 Functions to get random numbers rand () and rand (x)

Ps:a.rand (x) returns a random floating-point value of V, ranging from 0 to 1. If an integer parameter x has been established, it is used as a seed value to produce a repeating sequence.

B. rand () with no parameters has a different random value each time

C. When the rand () parameter is identical, the same random number will be generated, and the random values produced by the different x are different

Mysql> SELECT rand (), RAND (), Rand (), +--------------------+--------------------+--------------------+| RAND ()             | RAND ()             | RAND ()             |+--------------------+--------------------+--------------------+| 0.0917864060884215 | 0.6539400337766298 | 0.9943409813515293 |+--------------------+--------------------+--------------------+1 row in Set (0.00 sec) mysql> SELECT rand (5), Rand (5), Rand (6), +---------------------+---------------------+--------------------+| RAND (5)             | RAND (5)             | RAND (6)            0.40613597483014313 | 0.40613597483014313 | 0.6563190842571847 |+---------------------+------- --------------+--------------------+1 row in Set (0.00 sec)

"MySQL function" MySQL 5.5 starting from scratch sixth chapter