ALTER COLUMN是SQL Server中的一个DDL(数据定义语言)命令,用于修改表中列的定义。通过ALTER COLUMN命令,我们可以修改列的数据类型、长度、默认值等属性。 ALTER COLUMN语句的基本语法 下面是ALTER COLUMN语句的基本语法: ALTERTABLEtable_nameALTERCOLUMNcolumn_name new_data_type[(length)]; 1. 2. 其中,table_name...
执行sql语句时,先运行内部sql子查询语句,在运行外部sql查询语句; 子查询可以放在from子句中,也可以放在where子句中,视具体情况而定; select 列名1,列名2,... from (select 查询语句) as X; 1. 2. 3. 练习 #使用子查询按性别汇总人数 使用子查询时常常和in,all,any结合使用,...in(子查询);...all(子...
ALTERTABLE[schema_name.]table_nameADDcolumn_name1 data_typeconstraint,column_name2 data_typeconstraint...column_nameN data_typeconstraint; The following adds a new columnAddressof typevarcharand size 500 column to theEmployeetable. ALTERTABLEdbo.EmployeeAddAddressvarchar(500)NOTNULL; The following ad...
CREATE TABLE dbo.doc_exy (col_a varchar(5) UNIQUE NOT NULL, col_b decimal (4,2)) ; GO INSERT INTO dbo.doc_exy VALUES ('Test', 99.99) ; GO -- Verify the current column size. SELECT name, TYPE_NAME(system_type_id), max_length, precision, scale FROM sys.columns WHERE object_id...
\Program Files\Microsoft SQL Server\MSSQL13.MSSQLSERVER\MSSQL\DATA\t1dat3.ndf',SIZE=5MB,MAXSIZE=100MB, FILEGROWTH =5MB ), (NAME= test1dat4, FILENAME ='C:\Program Files\Microsoft SQL Server\MSSQL13.MSSQLSERVER\MSSQL\DATA\t1dat4.ndf',SIZE=5MB,MAXSIZE=100MB, FILEGROWTH =5MB )TO...
Learn more about the Microsoft.SqlServer.TransactSql.ScriptDom.AlterTableAlterColumnStatement.AlterTableAlterColumnStatement in the Microsoft.SqlServer.TransactSql.ScriptDom namespace.
To view the IGNORE_DUP_KEY setting for an index, use the ignore_dup_key column in the sys.indexes catalog view. In backward compatible syntax, WITH IGNORE_DUP_KEY is equivalent to WITH IGNORE_DUP_KEY = ON. STATISTICS_NORECOMPUTE = { ON | OFF } Disable or enable the automatic statistics...
其中包括用户定义类型变量或函数以及用户定义函数,但不能引用 Transact-SQL 语句。 partition_number 必须存在,否则,该语句将失败。 WITH ( <single_partition_rebuild_index_option> ) SORT_IN_TEMPDB、MAXDOP、DATA_COMPRESSION和XML_COMPRESSION 是使用 (PARTITION = partition_number) 语法重新生成单个分区时可以指定...
CREATE TABLE dbo.doc_exy (col_a varchar(5) UNIQUE NOT NULL, col_b decimal (4,2)) ; GO INSERT INTO dbo.doc_exy VALUES ('Test', 99.99) ; GO -- Verify the current column size. SELECT name, TYPE_NAME(system_type_id), max_length, precision, scale FROM sys.columns WHERE object_id...
mysql>ALTERTABLEsbtest1ADDCOLUMNpad6varchar(4990),ALGORITHM=INSTANT;ERROR1118(42000):Row size too large.The maximum row sizeforthe used table type,not counting BLOBs,is65535.This includes storage overhead,check the manual.You have to change some columns toTEXTor BLOBs ...