有时候我们在drop column的时候,会遇到一些default constraints而不能drop,如果我们已经知道constraint name,则可以用下面的语句先把constraint remove掉,然后再drop column。 declare@sqlnvarchar(1024) set@sql=N'alter table [system] drop constraint DF_
有时候我们在drop column的时候,会遇到一些default constraints而不能drop,如果我们已经知道constraint name,则可以用下面的语句先把constraint remove掉,然后再drop column。 declare@sqlnvarchar(1024) set@sql=N'alter table [system] drop constraint DF_system_LastGraceDate' execsp_executesql@sql 如果我们不知道c...
ALTER TABLE table_name DROP CONSTRAINT constraint_name 其具体使用参见第10章表的约束、索引与视图。★ 注意 ★使用ALTER TABLE修改表时要特别慎重,因为有些操作对数据库影响很大,且是不可逆的。如果用户采用DROP COLUMN关键字删除表中的某列,则该列所有已经存在的数据记录均被删除了。
Since we can specify constraints on a table, there needs to be a way to remove this constraint as well. In SQL, this is done via the ALTER TABLE statement. The SQL syntax to remove a constraint from a table is, ALTER TABLE "table_name" DROP [CONSTRAINT|INDEX] "CONSTRAINT_NAME";...
Sometimes we will wish to delete a column from an existing table in SQL. To do this, we specify that we want to change the table structure via the ALTER TABLE command, followed by a specification indicating that we want to remove a column. The detailed syntax for each database is as fo...
CREATETABLEdbo.soSessionC ( Column1INTNOTNULL, Column2NVARCHAR(4000)NULL, SpidFilterSMALLINTDEFAULT(@@spid)NOTNULL,CONSTRAINTCHK_soSessionC_SpidFilterCHECK(SpidFilter = @@spid),INDEXix_SpidFiler NONCLUSTERED (SpidFilter)-- INDEX ix_SpidFilter HASH-- (SpidFilter) ...
[CONSTRAINTconstraint_name] { [NULL|NOTNULL] {PRIMARYKEY|UNIQUE} [CLUSTERED|NONCLUSTERED] [WITHFILLFACTOR= fillfactor ] [WITH(index_option[, ...n ] ) ] [ON{partition_scheme_name(partition_column_name) | filegroup |"default"} ] | [FOREIGNKEY]REFERENCES[schema_name. ]referenced_table_name[...
ALTER TABLE DROP CONSTRAINT ALTER TABLE 或 CREATE TABLE .. CLUSTER BY 條款 ALTER TABLE 管理 COLUMN ALTER TABLE 管理 PARTITION ALTER TABLE 或 CREATE TABLE .. MASK 子句 ALTER TABLE 或 CREATE TABLE .. ROW FILTER 條款 ALTER VIEW ALTER VOLUME COMMENT ON CREATE CATALOG CREATE CONNECTION CREATE DATA...
开发中遇到程序报错,错误信息:SQLSTATE[23000]: Integrity constraint violation: 1048 Column ‘xxx’ cannot be null,这是因为我们要更新的字段设置了not null约束。 解决办法是根据实际情况,取消字段的not null约束或者给字段设置默认值。 一般在开发中,推荐根据如下情况进行设置: ...
Is a column in parentheses referenced by the new FOREIGN KEY constraint. ON DELETE {NO ACTION| CASCADE | SET NULL | SET DEFAULT } Specifies what action happens to rows in the table that is altered, if those rows have a referential relationship and the referenced row is deleted from the pa...