如何在DB2中查找约束列

Question

我想知道属于每个唯一约束的列（名称）。我可以在syscat.tabconst中轻松找到约束和表名。但是我找不到列名称。

Answer 1

我猜您正在从索引中寻找唯一约束。这是我过去用来查找特定表的查询。您应该能够根据所需的内容适应所需的内容：

SELECT
     T.TABSCHEMA AS TABLE_SCHEMA
    ,T.TABNAME   AS TABLE_NAME
    ,CASE T.TYPE
        WHEN 'F' THEN 'Foreign Key'
        WHEN 'I' THEN 'Functional Dependency'
        WHEN 'K' THEN 'Check'
        WHEN 'P' THEN 'Primary Key'
        WHEN 'U' THEN 'Unique'
     END AS Type
    ,I.INDSCHEMA AS INDEX_SCHEMA
    ,I.INDNAME   AS INDEX_NAME
    ,U.COLNAME   AS COLUMN_NAME
    ,U.COLSEQ    AS COLUMN_ORDINAL
    ,CASE U.COLORDER 
        WHEN 'A' THEN 'Ascending'
        WHEN 'D' THEN 'Descending'
        WHEN 'I' THEN 'Included (unordered)'
     END AS COLUMN_SORRING
FROM SYSCAT.TABCONST T
JOIN SYSCAT.CONSTDEP C
  ON T.CONSTNAME = C.CONSTNAME
JOIN SYSCAT.INDEXES I 
  ON C.BSCHEMA = I.INDSCHEMA
 AND C.BNAME   = I.INDNAME
JOIN SYSCAT.INDEXCOLUSE U
  ON I.INDSCHEMA = U.INDSCHEMA
 AND I.INDNAME   = U.INDNAME
WHERE T.TABSCHEMA = @schema
  AND T.TABNAME   = @table
  AND C.BTYPE     = 'I' --Indexes Only
ORDER BY 
     T.TABSCHEMA
    ,T.TABNAME
    ,I.INDSCHEMA
    ,I.INDNAME
    ,U.COLSEQ

以下是有关表的信息中心文章：

SYSCAT.TABCONST

SYSCAT.CONSTDEP

SYSCAT.INDEXES

SYSCAT.INDEXCOLUSE