SQL - 如何從表中獲取唯一鍵的列名

Question

我知道如何使用以下SQL語句從表中獲取列：

SELECT COLUMN_NAME 
FROM INFORMATION_SCHEMA.COLUMNS 
WHERE (TABLE_NAME = 'MYTABLENAME')

但是，我如何才能返回UNIQUE Key的列名？

Answer 1

select CCU.CONSTRAINT_NAME, CCU.COLUMN_NAME
from INFORMATION_SCHEMA.TABLE_CONSTRAINTS as TC
inner join INFORMATION_SCHEMA.CONSTRAINT_COLUMN_USAGE as CCU
    on TC.CONSTRAINT_CATALOG = CCU.CONSTRAINT_CATALOG
    and TC.CONSTRAINT_SCHEMA = CCU.CONSTRAINT_SCHEMA
    and TC.CONSTRAINT_NAME = CCU.CONSTRAINT_NAME
where TC.CONSTRAINT_CATALOG = 'MyCatalogName'
and TC.CONSTRAINT_SCHEMA = 'MySchemaName'
and TC.TABLE_NAME = 'MyTableName'
and TC.CONSTRAINT_TYPE = 'UNIQUE'

請記住，表可能有多個唯一約束，每個約束包含多個列。 您需要應用一些額外的邏輯來選擇正確的邏輯。

更新 - 基於其他評論......

上面的查詢將找到所有UNIQUE鍵約束。 但是，它不會找到PRIMARY KEY約束或在UNIQUE鍵約束之外創建的UNIQUE索引。

要查找主鍵，請將最后一行替換為：

and TC.CONSTRAINT_TYPE = 'PRIMARY KEY'

Answer 2

像這樣的東西可能有效（未經測試）：

SELECT *
FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS TC
WHERE TC.TABLE_NAME = 'MYTABLENAME'
AND TC.CONSTRAINT_TYPE = 'UNIQUE'

Answer 3

像這樣的東西：

Select col.name From 
sys.objects obj 
Join sys.columns col on col.[object_id] = obj.[object_id]
Join sys.index_columns idx_cols on idx_cols.[column_id] = col.[column_id] and idx_cols.[object_id] = col.[object_id]
Join sys.indexes idx on idx_cols.[index_id] = idx.[index_id] and idx.[object_id] = col.[object_id]
where obj.name = 'MYTABLENAME'
and idx.is_unique = 1

Answer 4

我發現工作的兩個是以下，第二個來自原始海報，但沒有TC.CONSTRAINT_TYPE ='UNIQUE'。 那條件不起作用

SELECT     col.name
FROM         sys.objects AS obj INNER JOIN
                      sys.columns AS col ON col.object_id = obj.object_id INNER JOIN
                      sys.index_columns AS idx_cols ON idx_cols.column_id = col.column_id AND idx_cols.object_id = col.object_id INNER JOIN
                      sys.indexes AS idx ON idx_cols.index_id = idx.index_id AND idx.object_id = col.object_id
WHERE     (obj.name = 'pluginUsers') AND (idx.is_unique = 1)

並且

SELECT     CCU.CONSTRAINT_NAME, CCU.COLUMN_NAME
FROM         INFORMATION_SCHEMA.TABLE_CONSTRAINTS AS TC INNER JOIN
                      INFORMATION_SCHEMA.CONSTRAINT_COLUMN_USAGE AS CCU ON TC.CONSTRAINT_CATALOG = CCU.CONSTRAINT_CATALOG AND 
                      TC.CONSTRAINT_SCHEMA = CCU.CONSTRAINT_SCHEMA AND TC.CONSTRAINT_NAME = CCU.CONSTRAINT_NAME
WHERE     (TC.TABLE_NAME = 'pluginUsers')

謝謝大家的帖子

Answer 5

不會DESCRIBE TABLE_NAME; 做訣竅？

Answer 6

SELECT * 
FROM mbiis.INFORMATION_SCHEMA.TABLE_CONSTRAINTS
WHERE TABLE_NAME='TABLE_NAME' AND CONSTRAINT_TYPE='UNIQUE';