{ PLAIN | EXTERNAL | EXTENDED | MAIN } ADD table_constraint [ NOT VALID ] ADD table_constraint_using_index ALTER CONSTRAINT constraint_name [ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ] VALIDATE CONSTRAINT constraint_name DROP CONSTRAINT [ IF EXISTS ] constraint_...
(一)添加字段 ALTER TABLE 表名 ADD 列名 列数据类型 DEFAULT 默认值; (二)判断字段不存在则添加 使用IF NOT EXISTS命令判断是否添加字段 ALTER TABLE 表名 ADD COLUMN IF NOT EXISTS 列名 列数据类型 DEFAULT 默认值; IF NOT EXISTS这个参数用法就是让查询时若该列不存在,则自动添加,若存在则什么也不做。因...
从MariaDB 10.0.2开始,ALTER TABLE还支持IF EXISTS和IF NOT EXISTS字句。包括以下几种情况: ADDCOLUMN[IFNOTEXISTS]ADDINDEX [IFNOTEXISTS]ADDFOREIGNKEY [IFNOTEXISTS]ADDPARTITION[IFNOTEXISTS]CREATEINDEX [IFNOTEXISTS]DROPCOLUMN[IFEXISTS]DROPINDEX [IFEXISTS]DROPFOREIGNKEY [IFEXISTS]DROPPARTITION[IFEXISTS] CH...
alter table add column if not exists 文心快码 "alter table add column if not exists" 是一个在数据库管理系统(DBMS)中用于修改表结构的SQL语句,其功能是在表中添加一个新列,但仅当该列尚不存在时执行此操作。下面是对你问题的详细回答: 解释"alter table add column if not exists"的SQL语法功能: ...
{ PLAIN | EXTERNAL | EXTENDED | MAIN } ADD table_constraint [ NOT VALID ] ADD table_constraint_using_index ALTER CONSTRAINT constraint_name [ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ] VALIDATE CONSTRAINT constraint_name DROP CONSTRAINT [ IF EXISTS ] constraint_...
] type_name REBUILD [ [ NONCLUSTERED ] WITH ( BUCKET_COUNT = bucket_count ) ] } | ADD { <column_definition> | <computed_column_definition> | <table_constraint> | <table_index> | <column_index> } [ ,...n ] | DROP [ { CONSTRAINT [ IF EXISTS ] { constraint_name } [ ,......
-- create the table as we want it to be CREATE TABLE IF NOT EXISTS tab_name ... ; -- if an older table version exists, update it ALTER TABLE name DROP COLUMN IF NOT EXISTS col_name col, DROP INDEX IF EXISTS idx_name; This feature is not compatible with Oracle MySQL, and MariaDB...
修改:ALTER TABLE 表名 ADD|CHANGE|DROP|MODIFY|RENAME COLUMN 列名 列的类型 [(长度) 约束] 删除:DROP TABLE IF EXISTS 表名; #一、库的管理 #库的创建 CREATE DATABASE IF NOT EXISTS books; 1. #库的修改 #修改库名(现在不能使用了,不安全。直接修改文件夹) ...
CreateExternalTableStatement CreateFederationStatement CreateFullTextCatalogStatement CreateFullTextIndexStatement CreateFullTextStopListStatement CreateFunctionStatement CreateIndexStatement CreateLoginSource CreateLoginStatement CreateMasterKeyStatement CreateMessageTypeStatement CreateOrAlterFunctionStatement Cre...
partition---age=11 age=12 age=15 >ALTERTABLEStudentInfoADDIFNOTEXISTSPARTITION(age=18);-- After adding a new partition to the table>SHOWPARTITIONSStudentInfo; partition---age=11 age=12 age=15 age=18-- Drop a partition from the table>SHOWPARTITIONSStudentInfo; partition---ag...