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MySQL筆記之數(shù)學函數(shù)詳解_MySQL教程

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推薦：MySQL筆記之別名的使用
在查詢時，可以為表和字段取一個別名。這個別名可以代替其指定的表和字段

絕對值函數(shù)ABS(x)和圓周率函數(shù)PI()

復制代碼 代碼如下:hl5o.cn

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)

平方根函數(shù)SQRT(x)和求余函數(shù)MOD(x,y)

復制代碼 代碼如下:hl5o.cn

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)

取整函數(shù)CEIL(x)、CEILING(x)和FLOOR(x)

復制代碼 代碼如下:hl5o.cn

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)和CEILING(x)返回大于或等于x的最小整數(shù)

FLOOR(x)返回小于或等于x的最大整數(shù)

隨機數(shù)函數(shù)RAND()和RAND(x)

復制代碼 代碼如下:hl5o.cn

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

RAND()和RAND(x)這兩個函數(shù)丟失返回0～1的隨機數(shù)

區(qū)別在于，RAND()返回的數(shù)是完全隨機的，而RAND(x)在x相同時返回的值相同

四舍五入函數(shù)ROUND(x)、ROUND(x,y)和TRUNCATE(x,y)

復制代碼 代碼如下:hl5o.cn

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)返回離x最近的整數(shù)，也就是對x進行四舍五入處理

ROUND(x,y)返回x保留到小數(shù)點后y位的值，在截取時進行四舍五入處理

復制代碼 代碼如下:hl5o.cn

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)返回x保留到小數(shù)點后y位的值，不進行四舍五入操作

符號函數(shù)SIGN(x)

復制代碼 代碼如下:hl5o.cn

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)返回x的符號，-1為負數(shù)，0不變，1為整數(shù)


冪運算函數(shù)POW(x,y)、POWER(x,y)

復制代碼 代碼如下:hl5o.cn

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

分享：MySQL筆記之子查詢使用介紹
子查詢是將一個查詢語句嵌套在另一個查詢語句中,內層查詢語句的查詢結果，可以為外層查詢語句提供查詢條件

來源：模板無憂//所屬分類：MySQL教程/更新時間：2013-05-04
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