在假设的场景中,我是一个没有表创建权限的用户。我想知道一个表中的某个列是否有唯一约束条件。我能否在字典中查找?我该如何操作?
除了检查唯一约束条件之外,还应另外执行此检查:
select count(*) from
USER_IND_COLUMNS cols
where cols.table_name='YOUR_TABLE_NAME'
and cols.COLUMN_NAME='YOUR_COLUMN';
要检查唯一约束,请使用已提供的方法:
select count(*) cnt
from user_constraints uc
where uc.table_name='YOUR_TABLE_NAME'
and uc.constraint_type='U';
或者您也可以查看ALL_CONSTRAINTS
和ALL_IND_COLUMNS
视图。
对于唯一约束,你可以这样做:
select cons.constraint_type,
all_cols.owner, all_cols.constraint_name,
all_cols.table_name,
all_cols.column_name,
all_cols.position
from all_cons_columns col
inner join all_cons_columns all_cols
on col.owner = all_cols.owner
and col.constraint_name = all_cols.constraint_name
inner join all_constraints cons
on col.owner = cons.owner
and col.constraint_name = cons.constraint_name
where col.owner = 'SCHEMA'
and col.table_name = 'FOO'
and col.column_name = 'ID'
and cons.constraint_type in ('U', 'P')
order by owner, constraint_name, position;
设置感兴趣的所有者、表和列,它将向您显示覆盖该列的所有约束。
注意,这不会显示在列上存在唯一索引的所有情况(因为可能存在唯一索引而没有约束存在的情况)。
示例:
SQL> create table foo(id number, id2 number, constraint foo_con unique(id, id2), constraint foo_con2 unique(id));
Table created.
现在列出所有涵盖id
的约束条件:
SQL> col column_name format a20
SQL> col constraint_name format a20
SQL> col table_name format a15
SQL> select cons.constraint_type,
2 all_cols.owner, all_cols.constraint_name,
3 all_cols.table_name,
4 all_cols.column_name,
5 all_cols.position
6 from all_cons_columns col
7 inner join all_cons_columns all_cols
8 on col.owner = all_cols.owner
9 and col.constraint_name = all_cols.constraint_name
10 inner join all_constraints cons
11 on col.owner = cons.owner
12 and col.constraint_name = cons.constraint_name
13 where col.owner = user
14 and col.table_name = 'FOO'
15 and col.column_name = 'ID'
16 and cons.constraint_type in ('U', 'P')
17 order by owner, constraint_name, position;
C OWNER CONSTRAINT_NAME TABLE_NAME COLUMN_NAME POSITION
- ------------------------------ -------------------- --------------- -------------------- ----------
U DTD_TRADE FOO_CON FOO ID 1
U DTD_TRADE FOO_CON FOO ID2 2
U DTD_TRADE FOO_CON2 FOO ID 1
select count(*) cnt
from user_constraints
where table_name=your_table_name
and constraint_type='U';
UNIQUE
约束;否则,在您的表上存在 UNIQUE
约束。这里是我刚尝试的一个查询。它列出了每个唯一性约束,由强制执行它的索引和唯一的列组成:
select x.index_name, c.column_name, c.column_position
from USER_INDEXES x join USER_IND_COLUMNS c
on x.index_name = c.index_name and x.table_name = c.table_name
left join USER_CONSTRAINTS uc
on x.index_name = uc.index_name and x.table_name = uc.table_name
where x.status = 'VALID' and
(x.uniqueness = 'UNIQUE' or
uc.constraint_type = 'U' and uc.status = 'ENABLED' and uc.validated = 'VALIDATED')
and x.table_name='<your table name_in_caps>'
order by x.index_name, c.column_position;
它似乎适用于主键、唯一索引和添加的唯一性约束。