SQL Server / T-SQL Constraints Default Value Set default value for column 1> 2> CREATE TABLE T ( 3> int1 int, 4> bit1 bit NOT NULL DEFAULT 0, 5> rvr1 timestamp, 6> usr1 nvarchar(28) DEFAULT USER, 7> createtime datetime DEFAULT CURRENT_TIMESTAMP 8> ) 9> GO 1> 2> INSERT...
truncate table**表名**删除整个表的记录,执行速度更快,用于清空大数据量表 注意,使用 truncate 前要确保数据可删除 select 语法结构(查询数据): 代码语言:javascript 代码运行次数:0 运行 AI代码解释 select*select_list*# 指定查询内容 into*new_table_name*# 把查询结果存放到一个新表中 from*table_name*# ...
创建日期=tt.Create_Date, 修改日期=tt.Modify_dateFROM( INFORMATION_SCHEMA.TABLES tINNERJOININFORMATION_SCHEMA.COLUMNS cONt.TABLE_NAME=c.TABLE_NAMEANDt.TABLE_TYPE='BASE TABLE'INNERJOIN(SELECTO.nameASis_name,PTB.value,C.column_id,C.nameASis_cname,PFD.valueASis_value,IDX.PrimaryKey,C.is_identity...
Single column foreign keys can also be specified at the column level. So the above statement could be rewritten as follows: USE Music; GO CREATE TABLE Artists ( ArtistId int IDENTITY(1,1) NOT NULL PRIMARY KEY, ArtistName nvarchar(255) NOT NULL, ActiveFrom date ); GO CREATE TABLE Albums ...
CREATETABLEMyTable ( mycolumnnn1nvarchar, mycolumn2nvarcharCOLLATEFrisian_100_CS_AS )WITH( CLUSTERED COLUMNSTOREINDEX) ; B. 指定列的 DEFAULT 约束 以下示例显示了为列指定默认值的语法。colA列具有名为constraint_colA的默认约束,默认值为0。 SQL ...
–1. IDENTIY 列不能为空,不能设默认值,创建后不能使用ALTER TABLE TableName ALTER COLUMN修改,每张表只能有一个自增列 –2. 查看当前值:SELECT IDENT_CURRENT(‘TableName’), — 查看增量值:SELECT IDENT_INCR(‘TableName’) — 查看原始种子值:SELECT IDENT_SEED(‘TableName’),起始值, TRUNCATE TAB...
CREATE TABLE 语句的语法格式为: CREATETABLE [ database_name.[owner]. |owner. ] table_name ( {<column_definition> |column_nameAScomputed_column_expression |<table_constraint> }[, n] ) [ON {filegroup | DEFAULT}] [TEXTIMAGE_ON {filegroup | DEFAULT}] ...
在这个表中,categoryid是主键,在CREATE TABLE语句末尾添加的CONSTRAINT子句告诉你它是一个主键。这个约束的名称是PK_Categories,你可以指定其它名称。 Another way of declaring a column as a primary key is to use the ALTER TABLE statement, which you could write as follows. ...
These two queries are functionally equivalent (because in this case there is a unique key on the BusinessEntityId column) and return the same set of results. As you can see the Person table is just accessed once in the revised query. The cost of the re-written query is also ~ 6 times...
[DEFAULTconstant_expression] |IDENTITY[ ( seed , increment ) ] ] [ROWGUIDCOL] [column_constraint] [ ...n ]<column_constraint>::={ [NULL|NOTNULL] | [PRIMARYKEY|UNIQUE] |CHECK(logical_expression) }<table_constraint>::={ {PRIMARYKEY|UNIQUE} (column_name[ , ...n ] ) |CHECK(logical...