mysql学习一（常用一些小函数）

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查看表结构

desc table;

show create table 表 \G;

repeat()函数

用来复制字符串,如下'ab'表示要复制的字符串，2表示复制的份数

mysql> select repeat('ab',2);

+----------------+
| repeat('ab',2) |
+----------------+
| abab |
+----------------+

1 row in set (0.00 sec)

又如
mysql> select repeat('a',2);

+---------------+
| repeat('a',2) |
+---------------+
| aa |
+---------------+
1 row in set (0.00 sec)

avg(),sum(),count(),max(),min() 统计函数

date_format(列，输出格式)

mysql> select date_format(build_time,'%Y%m%d') from logmgr_log limit 1;

+----------------------------------+
| date_format(build_time,'%Y%m%d') |
+----------------------------------+
| 20170414 |
+----------------------------------+

mysql> select date_format(build_time,'%Y%m%d') from logmgr_log limit 1;
+----------------------------------+
| date_format(build_time,'%Y%m%d') |
+----------------------------------+
| 20170414 |
+----------------------------------+

now()

mysql> select now() ;
+---------------------+
| now() |
+---------------------+
| 2017-05-18 18:45:23 |
+---------------------+

mid（）文本提取字符

mysql> select mid(build_time,1,10) from logmgr_log ;
+----------------------+
| mid(build_time,1,10) |
+----------------------+
| 2017-04-14 |
+----------------------+

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