1、删除外键约束，建立外键约束
先建立3个表：
-
/*
-
drop table tb
-
drop table tb_b
-
drop table tb_c
-
*/
-
-
--建立3个关联的表
-
create
table tb(
id
int primary
key ,vv
varchar(
10))
-
-
-
create
table tb_b(
-
idd
int primary
key,
-
id
int foreign
key
references tb(
id)
-
)
-
-
create
table tb_c(
-
iddd
int primary
key,
-
idd
int foreign
key
references tb_b(idd)
-
)
-
go
可以生成删除外键的语句，需要复制出来，然后放到再执行：
-
;WITH FK
--外键约束
-
AS
-
(
-
SELECT
-
SCH.name
as foreign_schema_name,
--外键schema名
-
FK.name
as foreign_name,
--外键名
-
FK.is_disabled ,
--是否禁用
-
-
FK.delete_referential_action_desc
as delete_action,
-
FK.update_referential_action_desc
as update_action,
-
-
FKC.constraint_column_id,
--约束列的id
-
FKC.parent_object_id,
--父对象的id
-
FKC.parent_column_id,
--父对象列的id
-
-
-
FKC.referenced_object_id,
--被引用的对象
-
FKC.referenced_column_id
--被引用的对象中的列
-
FROM sys.foreign_keys FK
-
INNER
JOIN sys.foreign_key_columns FKC
-
ON FK.object_id = FKC.constraint_object_id
-
INNER
JOIN sys.schemas SCH
-
ON FK.schema_id = SCH.schema_id
-
),
-
-
TB
--表和列
-
AS
-
(
-
SELECT
-
TB.object_id,
-
SCH.name
as schema_name,
-
TB.name
as table_name,
-
C.column_id
as column_id,
-
C.name
as column_name
-
FROM sys.tables TB
WITH(NOLOCK)
-
INNER
JOIN sys.columns C
WITH(NOLOCK)
-
ON TB.object_id = C.object_id
-
INNER
JOIN sys.schemas SCH
WITH(NOLOCK)
-
ON TB.schema_id = SCH.schema_id
-
WHERE TB.is_ms_shipped =
0
-- 此条件表示仅查询不是由内部 SQL Server 组件创建对象
-
)
-
-
SELECT
-
'alter table ['+TBP.schema_name+
'].['+TBP.table_name+
-
'] drop constraint ['+FK.foreign_name+
'];'
as
'删除外键的语句,复制出来后运行'
-
FROM FK
-
INNER
JOIN TB TBP
-
ON FK.parent_object_id = TBP.object_id
-
AND FK.parent_column_id = TBP.column_id
-
-
INNER
JOIN TB TBR
-
ON FK.referenced_object_id = TBR.object_id
-
AND FK.referenced_column_id = TBR.column_id
-
/*
-
删除外键的语句,复制出来后运行
-
alter table [dbo].[tb_b] drop constraint [FK__tb_b__id__6754599E];
-
alter table [dbo].[tb_c] drop constraint [FK__tb_c__idd__6C190EBB];
-
*/
另外，删除主键后，插入数据，然后再建立外键：
-
;WITH FK
--外键约束
-
AS
-
(
-
SELECT
-
SCH.name
as foreign_schema_name,
--外键schema名
-
FK.name
as foreign_name,
--外键名
-
FK.is_disabled ,
--是否禁用
-
-
FK.delete_referential_action_desc
as delete_action,
-
FK.update_referential_action_desc
as update_action,
-
-
FKC.constraint_column_id,
--约束列的id
-
FKC.parent_object_id,
--父对象的id
-
FKC.parent_column_id,
--父对象列的id
-
-
-
FKC.referenced_object_id,
--被引用的对象
-
FKC.referenced_column_id
--被引用的对象中的列
-
FROM sys.foreign_keys FK
-
INNER
JOIN sys.foreign_key_columns FKC
-
ON FK.object_id = FKC.constraint_object_id
-
INNER
JOIN sys.schemas SCH
-
ON FK.schema_id = SCH.schema_id
-
),
-
-
TB
--表和列
-
AS
-
(
-
SELECT
-
TB.object_id,
-
SCH.name
as schema_name,
-
TB.name
as table_name,
-
C.column_id
as column_id,
-
C.name
as column_name
-
FROM sys.tables TB
WITH(NOLOCK)
-
INNER
JOIN sys.columns C
WITH(NOLOCK)
-
ON TB.object_id = C.object_id
-
INNER
JOIN sys.schemas SCH
WITH(NOLOCK)
-
ON TB.schema_id = SCH.schema_id
-
WHERE TB.is_ms_shipped =
0
-- 此条件表示仅查询不是由内部 SQL Server 组件创建对象
-
)
-
-
SELECT
-
'alter table ['+TBP.schema_name+
'].['+TBP.table_name+
-
'] add constraint ['+FK.foreign_name+
'] '+
-
' foreign key('+TBP.column_name+
') references [' +
-
TBR.schema_name +
'].['+ TBR.table_name +
']('+TBR.column_name+
')'
-
as
'新建外键索引,复制然后在运行'
-
FROM FK
-
INNER
JOIN TB TBP
-
ON FK.parent_object_id = TBP.object_id
-
AND FK.parent_column_id = TBP.column_id
-
-
INNER
JOIN TB TBR
-
ON FK.referenced_object_id = TBR.object_id
-
AND FK.referenced_column_id = TBR.column_id
-
/*
-
新建外键索引,复制然后在运行
-
alter table [dbo].[tb_c] add constraint [FK__tb_c__idd__0A9D95DB] foreign key(idd) references [dbo].[tb_b](idd)
-
alter table [dbo].[tb_b] add constraint [FK__tb_b__id__05D8E0BE] foreign key(id) references [dbo].[tb](id)
-
*/
另外，还有一个问题：原来两个表之间是有外键的，删除了外键导入数据后，导入的数据记录条数和原表也一致，发现子表有记录不属于主表的，那么原来的外键是怎么建立的？
-
create
table tb(
id
int primary
key ,vv
varchar(
10))
-
-
insert
into tb
-
values(
1,
'aa')
-
go
-
-
create
table tb_b(
-
idd
int primary
key,
-
id
int
--foreign key references tb(id)
-
)
-
-
insert
into tb_b
-
values(
1,
2)
--id不在主表中
-
go
-
-
--新增外键约束,不会报错，with nocheck对于之前已经存在的数据，不会进行检测
-
ALTER
TABLE [dbo].[tb_b]
WITH
noCHECK
ADD FOREIGN
KEY([
id])
-
REFERENCES [dbo].[tb] ([
id])
-
GO
-
-
-
--会报错 ，在建立上面的约束后，再次插入，就会报错了
-
insert
into tb_b
-
values(
2,
2)
--id不在主表中
2、如何根据表名查询出创建该表的代码
-
--当用以下代码创建一个表后，如何根据表名查询出创建该表的代码(也就是以下代码)？
-
CREATE
TABLE [dbo].[a1](
-
[c2] [
decimal](
10,
2)
NULL,
-
[c3] [
decimal](
10,
3)
NULL
CONSTRAINT [DF_a1_c3]
DEFAULT ((
0)),
-
[re] [
bigint]
IDENTITY(
1,
1)
NOT
NULL,
-
CONSTRAINT [PK_a1] PRIMARY
KEY CLUSTERED
-
(
-
[re]
ASC
-
)
WITH (PAD_INDEX =
OFF, STATISTICS_NORECOMPUTE =
OFF, IGNORE_DUP_KEY =
OFF, ALLOW_ROW_LOCKS =
ON, ALLOW_PAGE_LOCKS =
ON)
ON [PRIMARY]
-
)
ON [PRIMARY]
-
go
-
declare @
sql
varchar(
8000),@tablename
varchar(
100)
-
set @tablename =
'a1'
--这里输入表名
-
set @
sql =
'create table ['+@tablename+
']
-
(
-
'
-
select @
sql = @
sql + b.name +
' '+
-
c.name+
-
case
when c.collation_name
is
not
null
then
'('+
-
case
when b.max_length <>
-1
then
convert(
varchar(
100),b.max_length)
-
else
'MAX'
-
end +
') '
-
else
''
-
end +
-
case
when b.is_identity =
1
then
' identity('+
convert(
varchar(
100),
IDENT_SEED(@tablename))+
','+
convert(
varchar(
100),
IDENT_INCR(@tablename))+
')'
else
''
end +
-
case
when d.definition
is
not
null
then
' default('+d.definition +
')'
else
''
end +
-
case
when b.is_nullable =
0
then
' not null'
else
' null'
end +
-
-
',
-
'
-
from sys.objects a
join sys.columns b
-
on a.object_id = b.object_id
-
join sys.types c
-
on b.system_type_id = c.system_type_id
and b.user_type_id = c.user_type_id
-
left
join sys.default_constraints d
-
on b.default_object_id = d.object_id
-
where a.name=@tablename
-
order
by b.column_id
-
if
exists(
select *
from sys.indexes
where object_id =object_id(@tablename)
and is_primary_key =
1 )
-
begin
-
select @
sql = @
sql +
'CONSTRAINT ['+
name+
'] PRIMARY KEY '+type_desc+
'
-
(
-
'
from sys.indexes
where object_id =object_id(@tablename)
and is_primary_key =
1
-
select @
sql = @
sql + b.name +
case
when a.is_descending_key =
1
then
' DESC'
else
' ASC'
end +
',
-
'
from sys.index_columns a
join sys.columns b
-
on a.object_id= b.object_id
and a.column_id = b.column_id
-
where a.object_id =object_id(@tablename)
-
select @
sql =
left(@
sql,
len(@
sql)
-3)+
'
-
)'
-
select @
sql = @
sql+
'
-
) ON [PRIMARY] '
-
end
-
else
-
begin
-
select @
sql =
left(@
sql,
len(@
sql)
-1)+
'
-
) ON [PRIMARY] '
-
end
-
print @
sql
-
-
/*
-
create table [a1]
-
(
-
c2 decimal null,
-
c3 decimal default(((0))) null,
-
re bigint identity(1,1) not null,
-
CONSTRAINT [PK_a1] PRIMARY KEY CLUSTERED
-
(
-
re ASC
-
)
-
) ON [PRIMARY]
-
-
*/
