ADD COLUMN new_column_name datatype; 以下SQL 语句在 employees 表中添加了一个名为 birth_date 的日期列: 实例 ALTERTABLEemployees ADDCOLUMNbirth_dateDATE; 2. 修改列的数据类型 实例 ALTERTABLETABLE_NAME MODIFYCOLUMNcolumn_name new_datatype; 以下SQL 语句将 employees 表中的 salary 列的数据类型修改为...
ALTERTABLEtable_nameADDPRIMARYKEY (column_name); 以下SQL 语句在 employees 表中添加了一个主键: 实例 ALTERTABLEemployees ADDPRIMARYKEY(employee_id); 6. 添加 FOREIGN KEY ALTERTABLEchild_tableADDCONSTRAINTfk_nameFOREIGNKEY (column_name)REFERENCESparent_table (column_name); 以下SQL 语句在 orders 表中添...
Flink SQL> show databases; +---+ | database name | +---+ | default_database | | alan_test | +---+ 2 rows in set Flink SQL> ALTER database default_catalog.alan_test set('createdate'='2023-11-20'); [INFO] Execute statement succeed. Flink SQL> show databases; +---+ | data...
SQL Server Management Studio can reuse connection information when opening multiple connections to Object Explorer and Query Editor windows. Close all connections to force reconnection. HASHED Applies to SQL Server logins only. Specifies that the password entered after the PASSWORD argument is already ...
ALTER INDEX修改索引是否可见,当索引状态为INVISIBLE时,SQL 优化器将不会选择该索引。 ADD [PARTITION]为分区表增加分区。OceanBase 数据库不支持将非分区表修改为分区表。 DROP {PARTITION | SUBPARTITION}删除分区: PARTITION:针对 Range、List 类型的一级分区,删除指定分区(如果指定分区下存在二级分区,会同时删除该分...
无为,多年 MySQL DBA 工作经验,现就职于某知名互联网公司,对 MySQL、 Redis、PostgrepSQL 等主流数据库有一定了解,拥有丰富的一线运维经验。 有没有一种途径能让我们随时能了解 alter table 语句的执行状况呢? 答案是肯定的,今天我们就来一起学习下 MySQL alter table 语句进度评估。 1 官方文档 首先我们来看下官...
mysql>ALTERTABLEsbtest1ADDCOLUMNc4int(10),ADDCOLUMNc5int(10),ALGORITHM=INSTANT;QueryOK,0rows affected,2warnings(0.10sec)Records:0Duplicates:0Warnings:2mysql>alter table sbtest1DROPCOLUMNc4,DROPCOLUMNc5,ALGORITHM=INSTANT;QueryOK,0rowsaffected(0.09sec)Records:0Duplicates:0Warnings:0 ...
对于数据库级别,使用 ALTER DATABASE SCOPED CONFIGURATION (Transact-SQL) 中的QUERY_OPTIMIZER_HOTFIXES 选项。 在查询级别,通过修改查询使用 USE HINT 'ENABLE_QUERY_OPTIMIZER_HOTFIXES' 查询提示。 在查询级别,在不更改代码的情况下,使用 USE HINT 'ENABLE_QUERY_OPTIMIZER_HOTFIXES' 并使用查询存储提示(预览版)功能...
To determine whether a database is in PROTECTED or UNPROTECTED mode, query the STANDBY_DATABASE column of the V$DATABASE dynamic performance view. REGISTER LOGFILE Clause Specify the REGISTER LOGFILE clause from the standby database to register log files from the failed primary. This operation ...
For more information, see Optimize index maintenance to improve query performance and reduce resource consumption. REORGANIZE isn't required in order to move the closed delta rowgroups into compressed rowgroups. The background tuple-mover (TM) process wakes up periodically to compress the closed delt...