MySQL 聚合函数
MySQL About 621 wordscount(*)
表示计算总行数,括号中写星与列名,结果是相同的
select count(*) from user;
max(列)
表示求此列的最大值
select max(age) from user;
+----------+
| max(age) |
+----------+
| 40 |
+----------+
1 row in set (0.00 sec)
min(列)
表示求此列的最小值
select min(age) from user where isdelete is not null;
+----------+
| min(age) |
+----------+
| 18 |
+----------+
1 row in set (0.00 sec)
sum(列)
表示求此列的和
select sum(age) from user;
+----------+
| sum(age) |
+----------+
| 281 |
+----------+
1 row in set (0.00 sec)
avg(列)
表示求此列的平均值
select avg(age) from user;
+----------+
| avg(age) |
+----------+
| 25.5455 |
+----------+
1 row in set (0.01 sec)
Views: 1,650 · Posted: 2019-04-06
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