DEFAULT CHARSET=utf8mb4; -- 查看表结构 DESCRIBE students; -- 或 SHOW COLUMNS FROM students; -- 修改表结构 ALTER TABLE students ADD COLUMN email VARCHAR(100); ALTER TABLE students MODIFY COLUMN name VARCHAR(100); ALTER TABLE students DROP COLUMN email; -- 删除表 DROP TABLE [IF EXISTS] ...
You have a "huge" table, and you need to ALTER it. By "huge" I mean that the ALTER would take an unacceptable amount of time. Things you might want to do. and for which this is well suited: ⚈ Add/drop columns ⚈ Modify datatypes (INT -> BIGINT, SIGNED -> UNSIGNED) ⚈ M...
生成批量修改 char 为 varchar2select 'alter table '||a.TABLE_NAME||' modify '||a.COLUMN_NAME||' VARCHAR2('||data_length||');' from all_tab_columns a where a.data_type='CHAR' AND OWNER='用户名'; 通过rtrim 函数把数据右边的空格清除掉 update 表名set 列名1=rtrim(列名1); mysql...
See Section 21.6.12, “Online Operations with ALTER TABLE in NDB Cluster”. ALTER TABLE upgrades MySQL 5.5 temporal columns to 5.6 format for ADD COLUMN, CHANGE COLUMN, MODIFY COLUMN, ADD INDEX, and FORCE operations. This conversion cannot be done using the INPLACE algorithm because the table...
ALTER TABLE foo MODIFY COLUMN a ..., MODIFY COLUMN b ..., etc; It is usually more efficient to collect all your alters into one statement. Subject Written By Posted how to alter multiple columns siva shanmugam November 07, 2008 12:36AM ...
Multiple ADD, ALTER, DROP, and CHANGE clauses are permitted in a single ALTER TABLE statement, separated by commas. This is a MySQL extension to standard SQL, which permits only one of each clause per ALTER TABLE statement. For example, to drop multiple columns in a single statement, do ...
mysql> alter table t1 modify name varchar(20);#需要重新定义下字段namemysql> insert into t1 values('林'); mysql> select *fromt1;+---+ | name | +---+ |林 | +---+ps:不要忘记将数据库编码也改成utf8,这样以后在该数据库下创建表时,都默认utf8编码了#配置文件:http://blog.csdn.net/...
-- 创建表使用 CHAR 类型CREATETABLEusers(idINTPRIMARYKEY,usernameCHAR(20),country_codeCHAR(2),genderCHAR(1));-- 插入数据INSERTINTOusersVALUES(1,'john_doe ','US','M');-- 插入时尾部空格会被存储-- 查询时注意SELECT*FROMusersWHEREusername='john_doe';-- 能匹配,因为比较时忽略尾部空格 ...
1670HY000ER_BINLOG_UNSAFE_SYSTEM_TABLE该语句是不安全的,因为它使用常规日志,慢查询日志或Performance_schema表。这是不安全的,因为系统表在从站上可能有所不同。 1671HY000ER_BINLOG_UNSAFE_AUTOINC_COLUMNS语句是不安全的,因为它调用插入到AUTO_INCREMENT列中的触发器或存储函数。插入值无法正确记录。
删除了这些不建议使用的兼容性SQL模式:DB2,MAXDB,MSSQL,MYSQL323,MYSQL40,ORACLE,POSTGRESQL,NO_FIELD_OPTIONS,NO_KEY_OPTIONS,NO_TABLE_OPTIONS。不能再将它们分配给sql_mode系统变量或用作mysqldump --compatible选项的允许值 删除MAXDB意味着将CREATE TABLE或ALTER TABLE的TIMESTAMP数据类型视为TIMESTAMP,而不再视为...