Sql-server – How to go about type iterations in a SQL Query

sql servert-sql

I have a Dependency table that has a ParentID, ParentEntityType, ChildID, and ChildEntityType along with additional fields. The EntityTypes refer to a variety of object types (Nodes, Groups, Transactions, etc.) which are all stored on their respective tables with the ID being the key. These tables contains some additional fields that I need to grab (e.g. the Name of the node).

For example: a Dependency record, with omitted fields, looks like

My question is how to smartly go about going through all the types. What I came up with was a left join for each type filtered with a WHERE and coalescing the resulting mass but that seems awful and would need to be duplicated for the child. I feel there has to be a better way but I'm a bit stumped.

SELECT d.[Name] as DepName
      ,[ParentEntityType]
      ,[ParentNetObjectID]
      ,[ChildEntityType]
      ,[ChildNetObjectID]
      ,coalesce(con.Name, nod.Caption, trans.name, app.name) as [ParentName]
      ,coalesce(con.status, nod.status, trans.laststatus, app.Availability) as [ParentStatus]
FROM dbo.Dependencies as d
    LEFT JOIN (SELECT  c.ContainerID
        ,c.Status
        ,c.Name
        FROM dbo.containers as c) as con on d.ParentNetObjectID = con.ContainerID AND d.ParentEntityType = 'Orion.Groups'
   LEFT JOIN (SELECT n.NodeID... --A left Join for every flavor that looks the same as above
WHERE 1=1 --Not important for this
ORDER BY ParentName

Best Answer

I would just join the tables directly
Coalesce is fine here I think

SELECT d.[Name] as DepName
      ,[ParentEntityType]
      ,[ParentNetObjectID]
      ,[ChildEntityType]
      ,[ChildNetObjectID]
      ,coalesce(con.Name, nod.Caption, trans.name, app.name) as [ParentName]
      ,coalesce(con.status, nod.status, trans.laststatus, app.Availability) as [ParentStatus]
FROM dbo.Dependencies as d
LEFT JOIN dbo.containers as con 
  on d.ParentNetObjectID = con.ContainerID 
 AND d.ParentEntityType = 'Orion.Groups'
LEFT JOIN  ...  
ORDER BY ParentName

You could put the 3 tables in a view or cte

select "orion" as type, 
        c.ContainerID
       ,c.Status
       ,c.Name
 FROM dbo.containers as c 
union all 
...

Related Solutions

Sql-server – Getting the name of the column that was used in a join

There is no sys object or DMV that will give you such information. You'll have to build it yourself, for which you can have a look at the example below.

Let's prepare some tables and dummy data.

CREATE TABLE ROOTTABLE (FIRST_ID INT, SECOND_ID INT, THIRD_ID INT, ONESETTING_ID INT);
CREATE TABLE SECONDTABLE (SECOND_ID INT, SECONDSETTING_ID INT);
CREATE TABLE THIRDTABLE (THIRD_ID INT, FOURTH_ID INT, RANDSETTING_ID INT, THIRDSETTING_ID INT);
CREATE TABLE FOURTHTABLE (FOURTH_ID INT, ONESETTING_ID INT);
CREATE TABLE SETTINGTABLE (ID INT, VALUE Varchar(10));

INSERT ROOTTABLE VALUES (1,2,3,15),(1,1,1,12),(11,5,6,12);
INSERT SECONDTABLE VALUES (1,11),(2,15),(5,13);
INSERT THIRDTABLE VALUES (1,5,6,15),(6,7,8,15),(3,7,8,15);
INSERT FOURTHTABLE VALUES (5,15),(6,16),(7,17),(1,18);
INSERT SETTINGTABLE VALUES
  (11,'one'),
  (12,'two'),
  (13,'three'),
  (14,'four'),
  (15,'five'),
  (16,'six'),
  (17,'seven');

Here's the query with the MATCHES column to show where the JOIN condition was fulfilled from (SETS.ID = ?).

SELECT FIRST.FIRST_ID, SEC.SECOND_ID, TRD.THIRD_ID, FRTH.FOURTH_ID, SETS.ID, SETS.VALUE,
       STUFF((SELECT ','+SOURCE_TABLE
              FROM (VALUES
                    ('ROOTTABLE',   FIRST.ONESETTING_ID),  -- 1
                    ('SECONDTABLE', SEC.SECONDSETTING_ID), -- 2
                    ('THIRDTABLE',  TRD.THIRDSETTING_ID),  -- 3
                    ('THIRDTABLE',  TRD.RANDSETTING_ID),   -- 4
                    ('FOURTHTABLE', FRTH.ONESETTING_ID))   -- 5
                   X (SOURCE_TABLE, SOURCE_ID)
              WHERE X.SOURCE_ID = SETS.ID
              FOR XML PATH('')),1,1,'') MATCHES
FROM ROOTTABLE FIRST
LEFT JOIN SECONDTABLE SEC ON SEC.SECOND_ID = FIRST.SECOND_ID
LEFT JOIN THIRDTABLE TRD ON TRD.THIRD_ID = FIRST.THIRD_ID
LEFT JOIN FOURTHTABLE FRTH ON FRTH.FOURTH_ID = TRD.FOURTH_ID
LEFT JOIN SETTINGTABLE SETS 
     ON (SETS.ID = FIRST.ONESETTING_ID    -- 1
      OR SETS.ID = SEC.SECONDSETTING_ID   -- 2
      OR SETS.ID = TRD.THIRDSETTING_ID    -- 3
      OR SETS.ID = TRD.RANDSETTING_ID     -- 4
      OR SETS.ID = FRTH.ONESETTING_ID);   -- 5

Note that I have laid out the sources that could make the match (1-5) in both the VALUES rows constructor and ON clauses so that you can follow the pattern.

Results:

| FIRST_ID | SECOND_ID | THIRD_ID | FOURTH_ID | ID | VALUE |                          MATCHES |
-----------------------------------------------------------------------------------------------
|        1 |         2 |        3 |         7 | 15 |  five | ROOTTABLE,SECONDTABLE,THIRDTABLE |
|        1 |         2 |        3 |         7 | 17 | seven |                      FOURTHTABLE |
|        1 |         1 |        1 |         5 | 11 |   one |                      SECONDTABLE |
|        1 |         1 |        1 |         5 | 12 |   two |                        ROOTTABLE |
|        1 |         1 |        1 |         5 | 15 |  five |           THIRDTABLE,FOURTHTABLE |
|       11 |         5 |        6 |         7 | 12 |   two |                        ROOTTABLE |
|       11 |         5 |        6 |         7 | 13 | three |                      SECONDTABLE |
|       11 |         5 |        6 |         7 | 15 |  five |                       THIRDTABLE |
|       11 |         5 |        6 |         7 | 17 | seven |                      FOURTHTABLE |

Some things to note:

The multiple ORs in the JOIN mean that SETS.ID could be matched by any of the sources - the query shows them all comma separated.
Rows 3-5 with the leading columns (1, 1, 1, 5) match SETS.ID three times.

SQL Fiddle

For clarity, this other SQL Fiddle shows the additional *SETTING_ID columns that are used to match against SETS.ID.

Sql-server – Doing a left join and having every match include an extra null row

I see 3 ways to do this but all involve a UNION ALL:

your version`:

SELECT
    T1.C1, ....., T1.CN,
    T2.C1, ..., T2.CM
FROM
    Table1 T1 JOIN Table2 T2
        ON T1.Key1 = T2.Key1

UNION ALL

SELECT
    T1.C1, ..., T1.CN,
    NULL, ... NULL
FROM
    Table1 T1 ;

slightly changing the second part:

SELECT
    T1.C1, ....., T1.CN,
    T2.C1, ..., T2.CM
FROM
    Table1 T1 JOIN Table2 T2
        ON T1.Key1 = T2.Key1

UNION ALL

SELECT
    T1.C1, ....., T1.CN,
    T2.C1, ..., T2.CM
FROM
    Table1 T1 LEFT JOIN Table2 T2
        ON 0 = 1 ;                   -- FALSE

first a UNION, then join:

SELECT
    T1.C1, ....., T1.CN,
    T2.C1, ..., T2.CM
FROM
    Table1 T1 JOIN  
      ( SELECT * FROM T2
        UNION ALL
        SELECT NULL, ..., NULL
       ) AS T2
        ON T1.Key1 = T2.Key1 
        OR T2.Key1 IS NULL ;

I don't think there will be much difference in execution plans and efficiency but the first one seems more simple.

Best Answer

Related Solutions

Sql-server – Getting the name of the column that was used in a join

Sql-server – Doing a left join and having every match include an extra null row

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