sql查询约束

① sql server怎么查询某一表的某一字段是否有约束

示例:
CREATE TABLE AA (
BB INT UNIQUE
);
SELECT

tab.name AS [表名],
idx.name AS [约束名称],
col.name AS [约束列名]
FROM
sys.indexes idx
JOIN sys.index_columns idxCol
ON (idx.object_id = idxCol.object_id
AND idx.index_id = idxCol.index_id
AND idx.is_unique_constraint = 1)
JOIN sys.tables tab
ON (idx.object_id = tab.object_id)
JOIN sys.columns col
ON (idx.object_id = col.object_id
AND idxCol.column_id = col.column_id)
WHERE
tab.name = 'AA'
结果:
表名 约束名称 约束列名
AA UQ__AA__3214B5C34460231C BB

② SQL中用语句查看表列的约束以及解除约束

SELECT
USER_CONS_COLUMNS.CONSTRAINT_NAMEAS约束名,
USER_CONS_COLUMNS.TABLE_NAMEAS表名,
USER_CONS_COLUMNS.COLUMN_NAMEAS列名,
USER_CONS_COLUMNS.POSITIONAS位置,
CONSTRAINT_TYPE,
SEARCH_CONDITION
FROM
USER_CONSTRAINTS
JOINUSER_CONS_COLUMNS
ON(USER_CONSTRAINTS.CONSTRAINT_NAME
=USER_CONS_COLUMNS.CONSTRAINT_NAME)
WHERE
CONSTRAINT_TYPEIN('C','V','O');

其实主要就是看

USER_CONSTRAINTS与 USER_CONS_COLUMNS 这2个视图.

数据库管理员的话

可以看

DBA_CONSTRAINTS与 DBA_CONS_COLUMNS 这2个视图.

③ SQL数据库中如何查看约束有那些方法求指教。

可以从下面的数据字典中查询想要的约束信息

dba_constraints
dba_cons_columns

④ sql server 查询约束键在哪个表的脚本

查询一个表的所有外键
SELECT主键列ID=b.rkey
,主键列名=(=b.rkeyANDid=b.rkeyid)
,外键表ID=b.fkeyid
,外键表名称=object_name(b.fkeyid)
,外键列ID=b.fkey
,外键列名=(=b.fkeyANDid=b.fkeyid)
,级联更新=ObjectProperty(a.id,'CnstIsUpdateCascade')
,级联删除=ObjectProperty(a.id,'CnstIsDeleteCascade')
FROMsysobjectsa
joinsysforeignkeysbona.id=b.constid
joinsysobjectscona.parent_obj=c.id
wherea.xtype='f'ANDc.xtype='U'
andobject_name(b.rkeyid)='titles'

SELECT*
FROMinformation_schema.columns
WHERETABLE_CATALOG='数据库名'
ANDTABLE_NAME='表名'
ANDCOLUMN_NAME='列名'

select*
fromsyscolumns
whereid=object_id('tableName')andname='fieldName'

⑤ sql语句，怎么查看一个表中的所有约束

sp_mshelpcolumns student
如上可以看到该表的所有结构、约束、默认值等

⑥ sql查询表中的约束

exec sp_helpconstraint S

ALTER TABLE S DROP CONSTRAINT 你自己的约束名称;

⑦ sql 约束名

SQL 约束（Constraints）

• SQL 约束用于规定表中的数据规则。

• 如果存在违反约束的数据行为，行为会被约束终止。

• 约束可以在创建表时规定（通过 CREATE TABLE 语句），或者在表创建之后规定（通过 ALTER TABLE 语句）。

⑧ sqlserver数据库里怎么查找一个表里的约束，要查出 约束名、列名、约束类型用sql语句查询

主键约束
SELECT
tab.name AS [表名],
idx.name AS [主键名称],
col.name AS [主键列名]
FROM
sys.indexes idx
JOIN sys.index_columns idxCol
ON (idx.object_id = idxCol.object_id
AND idx.index_id = idxCol.index_id
AND idx.is_primary_key = 1)
JOIN sys.tables tab
ON (idx.object_id = tab.object_id)
JOIN sys.columns col
ON (idx.object_id = col.object_id
AND idxCol.column_id = col.column_id);

唯一约束
SELECT
tab.name AS [表名],
idx.name AS [约束名称],
col.name AS [约束列名]
FROM
sys.indexes idx
JOIN sys.index_columns idxCol
ON (idx.object_id = idxCol.object_id
AND idx.index_id = idxCol.index_id
AND idx.is_unique_constraint = 1)
JOIN sys.tables tab
ON (idx.object_id = tab.object_id)
JOIN sys.columns col
ON (idx.object_id = col.object_id
AND idxCol.column_id = col.column_id);

外键约束
select
oSub.name AS [子表名称],
fk.name AS [外键名称],
SubCol.name AS [子表列名],
oMain.name AS [主表名称],
MainCol.name AS [主表列名]
from
sys.foreign_keys fk
JOIN sys.all_objects oSub
ON (fk.parent_object_id = oSub.object_id)
JOIN sys.all_objects oMain
ON (fk.referenced_object_id = oMain.object_id)
JOIN sys.foreign_key_columns fkCols
ON (fk.object_id = fkCols.constraint_object_id)
JOIN sys.columns SubCol
ON (oSub.object_id = SubCol.object_id
AND fkCols.parent_column_id = SubCol.column_id)
JOIN sys.columns MainCol
ON (oMain.object_id = MainCol.object_id
AND fkCols.referenced_column_id = MainCol.column_id)

Check约束
SELECT
tab.name AS [表名],
chk.name AS [Check约束名],
col.name AS [列名],
chk.definition
FROM
sys.check_constraints chk
JOIN sys.tables tab
ON (chk.parent_object_id = tab.object_id)
JOIN sys.columns col
ON (chk.parent_object_id = col.object_id
AND chk.parent_column_id = col.column_id)

⑨ 如何写SQL查询一个约束条件的内容

在oracle中有两个系统表可以查询
user_constraints约束表，记录该用户的所有约束。如非空，索引等等。
user_cons_columns约束字段表，记录每个约束涉及到的所有字段。