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SQL学习笔记:函数

时间:2021-07-01 10:21:17 帮助过:20人阅读

  • SQL函数
  • AVG
    select AVG(col) AS avgvalue from tablename
    select col2 from tablename where col1>(select AVG(col1) from tablename)
  • COUNT 返回值不包含空值
    select COUNT(*) from tablename 返回行数
    select COUNT(DISTINCT col) from tablename 返回列的唯一值
  • FIRST 返回第一个值
    select FIRST(col) AS colname from tablename
  • LAST 返回最后一个值
    select LAST(col) AS colname from tablename
  • MAX 返回最大值
  • MIN 返回最小值
  • SUM 返回总和
  • GROUP BY
    select col1, sum(col2) from tablename GROUP BY col1
  • HAVING
    select custom, sum(price) from tablename where custom = ‘tom‘ or custom = ‘jerry‘ group by custom HAVING sum(price)>1000
  • UCASE 将字符转化为大写
    select UCASE(col) from tablename
  • LCASE 将字符转为小写
  • MID 提取字符
    select MID(col, 起始数字, 长度) from tablename
  • LEN 提取字符长度
  • ROUND 舍入指定位数
    select ROUND(col, 位数) from tablename
  • NOW 返回当前时间和日期
    select NOW() from tablename
  • FORMAT
    select FORMAT(now(), ‘YYYY-MM-DD‘) from tablename

SQL学习笔记:函数

标签:唯一值   div   gpo   包含   where   group by   日期   max   min   

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