mysql中修改表的默认编码和表中字段的编码

一个是修改表的编码格式的

ALTER TABLE `table` DEFAULT CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci;

但是虽然修改了表的编码格式，但是字段的编码格式并没有修改过来，又发现一条语句，作用是修改字段的编码格式

ALTER TABLE `tablename` CHANGE `字段名1` `字段名2` VARCHAR(36) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NOT NULL; 

最后找到这么一条语句，它可以修改一张表的所有字段的编码格式，顿时方便多了

ALTER TABLE TABLE_NAME CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci; 

Ps ：延伸一下，修改mysql中所有表，所有字段编码，需要用到存储过程

转换表字段编码的sql语句为：ALTER TABLE TABLE_NAME CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci;

CREATE PROCEDURE `pr_convert_dbtab_utf8`(IN dbName varchar(100))
 
BEGIN
 
    declare stop int default 0;
 
    declare tabCount int default 0;
 
    declare strSql varchar(1000);
 
    declare name varchar(100);
 
    declare cur CURSOR FOR select table_name from information_schema.tables where table_schema=dbName;
 
    declare CONTINUE HANDLER FOR SQLSTATE '02000' SET stop = null;
 
    OPEN cur;
 
    FETCH cur INTO name;
 
    WHILE ( stop is not null) DO
 
        set tabCount=tabCount+1;
 
        set strSql = concat('alter table `',name,'` convert to character set utf8');
 
        set @sql1 = strSql;
 
        prepare stmt_p from @sql1;
 
        execute stmt_p;
 
        FETCH cur INTO name;
 
    END WHILE;
 
    CLOSE cur;
 
    SELECT concat('table: ', tabCount);
 
END;

输入调用存储过程的命令，参数为需要转换的数据库名

mysql> call pr_convert_dbtab_utf8('jiradb');
 
+-----------------------------+
 
| concat('table: ', tabCount) |
 
+-----------------------------+
 
| table: 245                  |
 
+-----------------------------+
 
1 row in set
 
Query OK, 0 rows affected
 
mysql> 

如果修改被外键约束的列，临时关闭外键约束，当修改完成之后再将外键约束加回来。

SET FOREIGN_KEY_CHECKS = 0;

/* DO WHAT YOU NEED HERE */

SET FOREIGN_KEY_CHECKS = 1;