• mysql 字符串函数


    用sql久了, 自然就越发觉得sql的方便, 于是研究研究sql的内置函数

    1. CONCAT(S1, S2, Sn) 作用:连接S1,S2...为一个字符串

    例子:

    SELECT
        CONCAT(ProjectName, ProjectOrgan) AS uname
    FROM
        meta_project
    LIMIT 1;

    2. INSERT (str, x, y, instr)作用: 从某位置开始y个字符长度的替换

    SELECT
        INSERT(ProjectName, 3, 1, 'aa') AS uname
    FROM
        meta_project
    LIMIT 1;

    3. LOWER(str) 作用: 将字符串str中所有字符变为小写

    SELECT
        LOWER(ProjectName) AS uname
    FROM
        meta_project;

    4. UPPER(str)作用: 将字符串str中所有字符变为大写

    SELECT
        UPPER("abcd") AS uname
    FROM
        meta_project;

    5. LEFT(str, x) 作用: 返回字符串str最左边的x个字符

    SELECT
        LEFT("abcd", 3) AS uname
    FROM
        meta_project;

    6. RIGHT(str,x) 作用: 返回字符串str最右边的x个字符

    SELECT
        UPPER(RIGHT("abcd", 3)) AS uname
    FROM
        meta_project;

    7. LPAD(str, n, pad)用字符串pad对str最左边进行填充,直到长度为n个字符长

    SELECT
        LPAD("abcd", 8, '1') AS uname
    FROM
        meta_project;

    8. RPAD(str, pad)用字符串pad对str最右边进行填充,直到长度为n个字符长

    SELECT
        RPAD("abcd", 8, '1') AS uname
    FROM
        meta_project;

    9. LTRIM(str) 去掉字符串左侧的空格

    SELECT
        LTRIM("    abcde") AS uname
    FROM
        meta_project;

    10 . RTRIM(str) 作用: 去掉字符串右侧的空格

    SELECT
        RTRIM("    abcde    ") AS uname
    FROM
        meta_project;

    11. TRIM(str) 作用: 去掉目标字符串的开头和结尾的空格

    SELECT
        TRIM("    abcde    ") AS uname
    FROM
        meta_project;

    12. REPEAT(str, n)作用:str重复n次

    SELECT
        REPEAT("abcd", 3) AS uname
    FROM
        meta_project
    limit 1;

    13. REPLACE(str, a, b)作用: 替换

    SELECT
        REPLACE("abcd", 'a', 'd') AS uname
    FROM
        meta_project
    limit 1;

    14. STRCMP(s1, s2)作用:比较字符串s1和s2的ascii码值的大小

    SELECT
        STRCMP('a','b'),STRCMP('b','b'),STRCMP('c','b')
    FROM
        meta_project limit 1;

    15. SUBSTRING(str, x, y)作用: 提取索引x到y的的字符

    SELECT
        SUBSTRING("abcdefghigkl" FROM 1 FOR 5)
    FROM
        meta_project limit 1;

      

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  • 原文地址:https://www.cnblogs.com/renfanzi/p/8242714.html
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