Mathematical function of MySQL function summary

What is? mysql function ？

==============

The function means to return a value with a specific relationship to the input parameter value ,mysql Provides a large number of rich functions , Various functions will be often used in database management and data query and operation .

Various functions are mainly divided into the following types in terms of functions ：

• Mathematical functions

• String function

• Date and time functions

• Conditional judgment function

• System information function

• Encryption function and other functions

This article mainly introduces the relevant use methods of mathematical functions .

What is a mathematical function ？

Mathematical functions are mainly used to deal with numerical data , The main mathematical functions include the following functions ：

• Absolute value function

• Trigonometric functions

• Sine function

• cosine function

• Tangent function

• Cotangent function

• Logarithmic function

• Random functions, etc

If the function reports an error , The mathematical function will return null NULL.

Absolute value function ABS(x)

abs(x) return x The absolute value of ;

mysql> select abs(2), abs(-6.6), abs(-99), abs(3.000);
+--------+-----------+----------+------------+
| abs(2) | abs(-6.6) | abs(-99) | abs(3.000) |
+--------+-----------+----------+------------+
|      2 |       6.6 |       99 |      3.000 |
+--------+-----------+----------+------------+
1 row in set (0.00 sec)

mysql>

A function that returns pi PI()

PI() Return the PI π Value . The default display decimal places are the first 6 position .

mysql> select pi();
+----------+
| pi()     |
+----------+
| 3.141593 |
+----------+
1 row in set (0.00 sec)

mysql>

Square root function SQRT(x)

SQRT(x) Returns a non negative number x The square root of .

mysql> select sqrt(9), sqrt(30), sqrt(-30);
+---------+-------------------+-----------+
| sqrt(9) | sqrt(30)          | sqrt(-30) |
+---------+-------------------+-----------+
|       3 | 5.477225575051661 |      NULL |
+---------+-------------------+-----------+
1 row in set (0.00 sec)

mysql>

Find the cofunction MOD(x,y)

mod(x,y) return x By y The remainder after division ,mod() Values with decimal parts can also be calculated , He returns the exact remainder after the trigger operation .

mysql> select mod(31,10), mod(31.5,3), mod(-31,10);
+------------+-------------+-------------+
| mod(31,10) | mod(31.5,3) | mod(-31,10) |
+------------+-------------+-------------+
|          1 |         1.5 |          -1 |
+------------+-------------+-------------+
1 row in set (0.00 sec)

mysql>

Get the function of an integer CEIL(x)、CEILING(x) and FLOOR(x)

ceil(x) and ceiling(x) It means the same thing , Return no less than x The minimum integer value of , The return value is converted into a bigint.

mysql> select ceil(20), ceil(-3.33), ceiling(20), ceiling(-3.33);
+----------+-------------+-------------+----------------+
| ceil(20) | ceil(-3.33) | ceiling(20) | ceiling(-3.33) |
+----------+-------------+-------------+----------------+
|       20 |          -3 |          20 |             -3 |
+----------+-------------+-------------+----------------+
1 row in set (0.01 sec)

mysql>

floor(x) Return is no greater than x Maximum integer value ;

mysql> select floor(20), floor(-3.33);
+-----------+--------------+
| floor(20) | floor(-3.33) |
+-----------+--------------+
|        20 |           -4 |
+-----------+--------------+
1 row in set (0.00 sec)

mysql>

A function to get random numbers RAND() and RAND(x)

rand(x) Returns a random floating-point value , The scope is 0~1 Between , If you specify an overall parameter x, Then this x Used as seed value , Used to generate repeat sequences .

rand Without parameters

mysql> select rand(), rand(), rand();
+--------------------+---------------------+---------------------+
| rand()             | rand()              | rand()              |
+--------------------+---------------------+---------------------+
| 0.5348021588612368 | 0.19999561477452107 | 0.39557162802254003 |
+--------------------+---------------------+---------------------+
1 row in set (0.00 sec)

mysql>

You can see that each random value returned is different .

rand Add parameter

mysql> select rand(5), rand(5), rand();
+---------------------+---------------------+--------------------+
| rand(5)             | rand(5)             | rand()             |
+---------------------+---------------------+--------------------+
| 0.40613597483014313 | 0.40613597483014313 | 0.3778713265227818 |
+---------------------+---------------------+--------------------+
1 row in set (0.00 sec)

mysql>

You can see from above , If you use rand(x), And x The value of is the same , Then the generated random value , It's the same , conversely , Different x, The resulting random value , Not so .

function ROUND(x)、ROUND(x,y) and TRUNCATE(x,y)

round(x) Returns the closest parameter x The integer of , Yes x Values are rounded .

mysql> select round(-2.58), round(6.2), round(9.9);
+--------------+------------+------------+
| round(-2.58) | round(6.2) | round(9.9) |
+--------------+------------+------------+
|           -3 |          6 |         10 |
+--------------+------------+------------+
1 row in set (0.00 sec)

mysql>

round(x,y) Returns the closest parameter x Number of numbers , Its value is kept after the decimal point y position , if y negative , Will keep x To the left of the decimal point y position , Also use rounding .

mysql> select round(1.78, 1), round(1.99, 0), round(222.90, -1), round(222.90, -2), round(888.80, -2);
+----------------+----------------+-------------------+-------------------+-------------------+
| round(1.78, 1) | round(1.99, 0) | round(222.90, -1) | round(222.90, -2) | round(888.80, -2) |
+----------------+----------------+-------------------+-------------------+-------------------+
|            1.8 |              2 |               220 |               200 |               900 |
+----------------+----------------+-------------------+-------------------+-------------------+
1 row in set (0.00 sec)

mysql>

truncate(x,y) Returns the number after the decimal point is rounded off y Digit number x. if y The value of is 0, Then the result does not have a decimal point or a decimal part . if y Set to negative , Then cut off （ Zeroing ）x The third from the left of the decimal point y All the lower values after the beginning of the bit . The way that applies here is in Mathematics Go to the tail .

mysql> select truncate(1.22,1), truncate(1.66,1), truncate(666.66, -2), truncate(666.66,0);
+------------------+------------------+----------------------+--------------------+
| truncate(1.22,1) | truncate(1.66,1) | truncate(666.66, -2) | truncate(666.66,0) |
+------------------+------------------+----------------------+--------------------+
|              1.2 |              1.6 |                  600 |                666 |
+------------------+------------------+----------------------+--------------------+
1 row in set (0.00 sec)

mysql>

Symbolic function SIGN(x)

sign(x) Returns the symbol of the parameter ,x The value of is negative 、 Zero or exactly the return result corresponds to -1、0 perhaps 1.

Number type	negative	zero	Positive numbers
return	-1	0	1

mysql> select sign(-19), sign(-1.11), sign(0), sign(99);
+-----------+-------------+---------+----------+
| sign(-19) | sign(-1.11) | sign(0) | sign(99) |
+-----------+-------------+---------+----------+
|        -1 |          -1 |       0 |        1 |
+-----------+-------------+---------+----------+
1 row in set (0.00 sec)

mysql>

Power function POW(x,y)、POWER(x,y) and EXP(x)

pow(x,y) perhaps power(x,y) The function returns x Of y The resulting value of the power .

mysql> select pow(2,2), power(2,2), pow(3,3), power(3,3), pow(-0.5,2), power(-0.5,2);
+----------+------------+----------+------------+-------------+---------------+
| pow(2,2) | power(2,2) | pow(3,3) | power(3,3) | pow(-0.5,2) | power(-0.5,2) |
+----------+------------+----------+------------+-------------+---------------+
|        4 |          4 |       27 |         27 |        0.25 |          0.25 |
+----------+------------+----------+------------+-------------+---------------+
1 row in set (0.00 sec)

mysql>

exp(x) return e Of x The value after the power

mysql> select exp(3), exp(-3), exp(0);
+--------------------+----------------------+--------+
| exp(3)             | exp(-3)              | exp(0) |
+--------------------+----------------------+--------+
| 20.085536923187668 | 0.049787068367863944 |      1 |
+--------------------+----------------------+--------+
1 row in set (0.00 sec)

mysql>

Logarithm function LOG(x) and LOG10(x)

log(x) return x The natural logarithm of ,x Equivalent to base e The logarithmic .

mysql> select log(3), log(-3), log(9), log(-9), log(0);
+--------------------+---------+--------------------+---------+--------+
| log(3)             | log(-3) | log(9)             | log(-9) | log(0) |
+--------------------+---------+--------------------+---------+--------+
| 1.0986122886681098 |    NULL | 2.1972245773362196 |    NULL |   NULL |
+--------------------+---------+--------------------+---------+--------+
1 row in set, 3 warnings (0.00 sec)

mysql>

Since the domain of logarithm is >=0, So negative sum 0 All the returned results are null.

log10(x) return x Based on 10 The logarithmic ;

mysql> select log10(2), log10(100), log10(-100);
+--------------------+------------+-------------+
| log10(2)           | log10(100) | log10(-100) |
+--------------------+------------+-------------+
| 0.3010299956639812 |          2 |        NULL |
+--------------------+------------+-------------+
1 row in set, 1 warning (0.00 sec)

mysql>

It's a function of angle and radian RADIANS(x) and DEGREES(x)

radians(x) The parameter x From angle to radian ;

mysql> select radians(90), radians(100);
+--------------------+--------------------+
| radians(90)        | radians(100)       |
+--------------------+--------------------+
| 1.5707963267948966 | 1.7453292519943295 |
+--------------------+--------------------+
1 row in set (0.00 sec)

mysql>

degrees(x) The parameter x From radian to angle ;

mysql> select degrees(pi()), degrees(pi()/2);
+---------------+-----------------+
| degrees(pi()) | degrees(pi()/2) |
+---------------+-----------------+
|           180 |              90 |
+---------------+-----------------+
1 row in set (0.00 sec)

mysql>

Tips ：PI() Is the return of PI .

Sine function SIN(x) And anti sine functions ASIN(x)

sin(x) return x sine , among x Is the radian value ;

mysql> select sin(1), round(sin(pi()));
+--------------------+------------------+
| sin(1)             | round(sin(pi())) |
+--------------------+------------------+
| 0.8414709848078965 |                0 |
+--------------------+------------------+
1 row in set (0.00 sec)

mysql>

asin(x) return x The inverse sine of , That is, the sine is x Value . if x be not in -1 To 1 Within the scope of , Then return to null.

mysql> select asin(0.8414709848078965), asin(2);
+--------------------------+---------+
| asin(0.8414709848078965) | asin(2) |
+--------------------------+---------+
|                        1 |    NULL |
+--------------------------+---------+
1 row in set (0.00 sec)

mysql>

function ASIN and SIN They're inverse functions to each other .

cosine function COS(x) And arccosine functions ACOS(x)

cos(x) return x The cosine of , among x Is the radian value ;

mysql> select cos(0), cos(pi()), cos(1);
+--------+-----------+--------------------+
| cos(0) | cos(pi()) | cos(1)             |
+--------+-----------+--------------------+
|      1 |        -1 | 0.5403023058681398 |
+--------+-----------+--------------------+
1 row in set (0.00 sec)

mysql>

acos(x) return x The arccosine of , The cosine is x Value . if x be not in -1~1 Only within , Then return to null.

mysql> select acos(1), round(acos(0.5403023058681398));
+---------+---------------------------------+
| acos(1) | round(acos(0.5403023058681398)) |
+---------+---------------------------------+
|       0 |                               1 |
+---------+---------------------------------+
1 row in set (0.00 sec)

mysql>

function ACOS and COS They're inverse functions to each other .

Tangent function 、 Arctangent function and cotangent function

TAN(x) return x Tangent of , among x For a given radian value .

mysql> select tan(0.4), round(tan(pi()/4));
+--------------------+--------------------+
| tan(0.4)           | round(tan(pi()/4)) |
+--------------------+--------------------+
| 0.4227932187381618 |                  1 |
+--------------------+--------------------+
1 row in set (0.01 sec)

mysql>

ATAN(x) return x It's all right , That is, the tangent is x Value .

mysql> select atan(0.4227932187381618), atan(1);
+--------------------------+--------------------+
| atan(0.4227932187381618) | atan(1)            |
+--------------------------+--------------------+
|                      0.4 | 0.7853981633974483 |
+--------------------------+--------------------+
1 row in set (0.01 sec)

mysql>

function ATAN and TAN They're inverse functions to each other ;

COT(x) return x The cotangent of ;

mysql> select cot(0.3), 1/tan(0.3), cot(pi()/4);
+--------------------+--------------------+--------------------+
| cot(0.3)           | 1/tan(0.3)         | cot(pi()/4)        |
+--------------------+--------------------+--------------------+
| 3.2327281437658275 | 3.2327281437658275 | 1.0000000000000002 |
+--------------------+--------------------+--------------------+
1 row in set (0.00 sec)

mysql>

function cot and TAN Reciprocal functions .

thus , In this paper, the end .

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