SQL Query based on specific conditions

Question

Figure 1 denotes the current state of the TABLE A and TABLE B.

The current implementation is to fetch the new MIds to Table B and copy the SqlQuery from base process, in case of a new market or an existing market. Below query is used for this:

SELECT A.MId, B1.Loop, B1.Segment, B1.SqlQuery, B1.UseDefault
FROM TableB B1 WITH (NOLOCK)
INNER JOIN TableA A WITH (NOLOCK) ON B1.MId IN (100, 200) 
                                  AND B1.MId = A.BaseMarket 
                                  AND ISNULL(A.POCId, 0) > 0
LEFT JOIN TableB B2 WITH (NOLOCK) ON A.MId = B2.MId
WHERE B2.MId IS NULL

Figure 2 shows the updated data in Table A and the desired state of Table B. The required implementation would be:

1. To fetch the new MIds to Table B and copy the SqlQuery from Base Process, if it's a new market (XYZ Market - 2001, 2002)
2. If the market configuration already exists in Table B (Market ABC - 1001 and 1002), then copy the existing configuration's SqlQuery.

Here's the complete flow for Table A and B. The base configurations (100 and 200) in both tables were inserted manually initially including the loop and segments.

1. A new market is introduced and a new MId is created in Table A. Let's assume that to be 1001 and 1002 for Market ABC.

2. Corresponding records are inserted in Table B for each MId and it copies data from Base Configuration in Table B. Inserted Records (SqlId - 3 and 4)

3. SqlQuery column in Table B is updated manually due to a specific business request. (SqlId - 3 and 4). Hence, the different query.

4. Market ABC is updated in front end, which creates two new entries in Table A. (MId - 1003 and 1004). Also, new market XYZ (MId - 2001 and 2002) is created.

5. Corresponding entries created in Table B should refer Base Configuration for Market XYZ (SqlId - 7 and 8), since it's a new market but should copy the existing configuration for Market ABC (MId - 1001 and 1002) since it's configuration already existed.

I am looking for a suggestions if a single query can implement this requirement using Case statement. I'll appreciate your help!

Answer 1

I guess by market configuration already exists you actually mean the combination of MarketName and Type . So here's the query

SELECT
  A.NewId, B.Loop, B.Segment, B.SqlQuery, B.UseDefault
FROM (
  SELECT
    A1.MId AS NewId, A2.MId AS RefId
  FROM
    TableA A1
  INNER JOIN
    TableA A2
  ON
    (A1.MarketName = A2.MarketName AND A1.Type = A2.Type) -- use your market configuration logic here
  OR
    A1.BaseMarket = A2.BaseMarket
  WHERE
    A1.Mid NOT IN (SELECT MId FROM TableB)
) As A
INNER JOIN
  TableB B
ON (A.RefId = B.MID)

At first we are self-joining TableA to get the reference MId as RefId here. Then we are joining the new derived table with TableB .

Hope this helps. Thank you!