Mathematical function explanation of MySQL notes

The absolute value function ABS(x) and the PI function PI()

mysql> SELECT ABS(0.5), ABS(-0.5), PI();
+----------+-----------+----------+
| ABS(0.5) | ABS(-0.5) | PI()     |
+----------+-----------+----------+
|      0.5 |       0.5 | 3.141593 |
+----------+-----------+----------+
 row in set (0.00 sec)

The square root function SQRT(x) and the remainder function MOD(x,y)

mysql> SELECT SQRT(16), SQRT(3), MOD(13,4);
+----------+--------------------+-----------+
| SQRT(16) | SQRT(3)            | MOD(13,4) |
+----------+--------------------+-----------+
|        4 | 1.7320508075688772 |         1 |
+----------+--------------------+-----------+
 row in set (0.00 sec)

Rounding functions CEIL(x), CEILING(x), and FLOOR(x)

mysql> SELECT CEIL(2.3), CEIL(-2.3), CEILING(2.3), CEILING(-2.3);
+-----------+------------+--------------+---------------+
| CEIL(2.3) | CEIL(-2.3) | CEILING(2.3) | CEILING(-2.3) |
+-----------+------------+--------------+---------------+
|         3 |         -2 |            3 |            -2 |
+-----------+------------+--------------+---------------+
 row in set (0.00 sec)
mysql> SELECT FLOOR(2.3), FLOOR(-2.3);
+------------+-------------+
| FLOOR(2.3) | FLOOR(-2.3) |
+------------+-------------+
|          2 |          -3 |
+------------+-------------+
 row in set (0.00 sec)

CEIL(x) and CEILING(x) return the smallest integer greater than or equal to x

FLOOR(x) returns the maximum integer less than or equal to x

Random number functions RAND() and RAND(x)

mysql> SELECT RAND(), RAND(2), RAND(2);
+--------------------+--------------------+--------------------+
| RAND()             | RAND(2)            | RAND(2)            |
+--------------------+--------------------+--------------------+
| 0.8269294489425881 | 0.6555866465490187 | 0.6555866465490187 |
+--------------------+--------------------+--------------------+
 row in set (0.00 sec)

The functions RAND() and RAND(x) are missing random Numbers that return 0 to 1

The difference is that RAND() returns a completely random number, while RAND(x) returns the same value at x

4 rounding 5 into the functions ROUND(x), ROUND(x,y) and TRUNCATE(x,y)

mysql> SELECT ROUND(2.3), ROUND(2.5), ROUND(2.53,1), ROUND(2.55,1);
+------------+------------+---------------+---------------+
| ROUND(2.3) | ROUND(2.5) | ROUND(2.53,1) | ROUND(2.55,1) |
+------------+------------+---------------+---------------+
|          2 |          3 |           2.5 |           2.6 |
+------------+------------+---------------+---------------+
 row in set (0.00 sec)

ROUND(x) returns the nearest integer to x, which is x rounded by 4 and 5

ROUND(x,y) returns the value of x reserved to the y bit after the decimal point, and is rounded 4 and 5 when intercepting

mysql> SELECT TRUNCATE(2.53,1), TRUNCATE(2.55,1);
+------------------+------------------+
| TRUNCATE(2.53,1) | TRUNCATE(2.55,1) |
+------------------+------------------+
|              2.5 |              2.5 |
+------------------+------------------+
 row in set (0.00 sec)

TRUNCATE(x,y) returns the value of x reserved to the y place after the decimal point, no rounding of 4 or 5

Sign function SIGN(x)

mysql> SELECT SIGN(-2), SIGN(0), SIGN(2);
+----------+---------+---------+
| SIGN(-2) | SIGN(0) | SIGN(2) |
+----------+---------+---------+
|       -1 |       0 |       1 |
+----------+---------+---------+
 row in set (0.00 sec)

SIGN(x) returns the symbol x, minus 1 is a negative number, 0 is unchanged, and 1 is an integer

Power operation functions POW(x,y), POWER(x,y)

mysql> SELECT POW(3,2), POWER(3,2);
+----------+------------+
| POW(3,2) | POWER(3,2) |
+----------+------------+
|        9 |          9 |
+----------+------------+
 row in set (0.00 sec)