Thursday, June 24, 2010

SQL Identifying Foreign Keys

In the past I've got a few legacy systems to maintain and improve, some of them with good documentation, some of them with non-existing documentation some even my own which were left alone for too long before I was able to document them.


This great article, written by Greg Robidoux has been an invaluable help in determining relationships in SQL, thank you Greg!


I've removed a few fields and left with this:


SELECT --PKTABLE_QUALIFIER = CONVERT(SYSNAME,DB_NAME()), 
       --PKTABLE_OWNER = CONVERT(SYSNAME,SCHEMA_NAME(O1.SCHEMA_ID)), 
       PKTABLE_NAME = CONVERT(SYSNAME,O1.NAME), 
       PKCOLUMN_NAME = CONVERT(SYSNAME,C1.NAME), 
       --FKTABLE_QUALIFIER = CONVERT(SYSNAME,DB_NAME()), 
       --FKTABLE_OWNER = CONVERT(SYSNAME,SCHEMA_NAME(O2.SCHEMA_ID)), 
       FKTABLE_NAME = CONVERT(SYSNAME,O2.NAME), 
       FKCOLUMN_NAME = CONVERT(SYSNAME,C2.NAME), 
       -- Force the column to be non-nullable (see SQL BU 325751) 
       --KEY_SEQ             = isnull(convert(smallint,k.constraint_column_id), sysconv(smallint,0)), 
       UPDATE_RULE = CONVERT(SMALLINT,CASE OBJECTPROPERTY(F.OBJECT_ID,'CnstIsUpdateCascade')  
                                        WHEN 1 THEN 0 
                                        ELSE 1 
                                      END), 
       DELETE_RULE = CONVERT(SMALLINT,CASE OBJECTPROPERTY(F.OBJECT_ID,'CnstIsDeleteCascade')  
                                        WHEN 1 THEN 0 
                                        ELSE 1 
                                      END), 
       FK_NAME = CONVERT(SYSNAME,OBJECT_NAME(F.OBJECT_ID)), 
       PK_NAME = CONVERT(SYSNAME,I.NAME), 
       DEFERRABILITY = CONVERT(SMALLINT,7)   -- SQL_NOT_DEFERRABLE 
FROM   SYS.ALL_OBJECTS O1, 
       SYS.ALL_OBJECTS O2, 
       SYS.ALL_COLUMNS C1, 
       SYS.ALL_COLUMNS C2, 
       SYS.FOREIGN_KEYS F 
       INNER JOIN SYS.FOREIGN_KEY_COLUMNS K 
         ON (K.CONSTRAINT_OBJECT_ID = F.OBJECT_ID) 
       INNER JOIN SYS.INDEXES I 
         ON (F.REFERENCED_OBJECT_ID = I.OBJECT_ID 
             AND F.KEY_INDEX_ID = I.INDEX_ID) 
WHERE  O1.OBJECT_ID = F.REFERENCED_OBJECT_ID 
       AND O2.OBJECT_ID = F.PARENT_OBJECT_ID 
       AND C1.OBJECT_ID = F.REFERENCED_OBJECT_ID 
       AND C2.OBJECT_ID = F.PARENT_OBJECT_ID 
       AND C1.COLUMN_ID = K.REFERENCED_COLUMN_ID
       AND C2.COLUMN_ID = K.PARENT_COLUMN_ID
order by PKTABLE_NAME, FKTABLE_NAME

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