Need help to simplify this T-SQL query - sql

Question

I have this working T-SQL query, is there any way to simplify it?
The SELECT COUNT(*) FROM Tablename is repeating and only the condition is different for each query, so is there a way to simplify this more? thank you
SELECT COUNT(*) FROM Table
WHERE columnA = 'I' AND columnB = 'I' AND columnC =''
UNION ALL
SELECT COUNT(*) FROM Table
WHERE columnA = 'I' AND columnB = 'I' AND columnC <>''
UNION ALL
SELECT COUNT(*) FROM Table
WHERE columnA IN ('A','R') AND columnB = 'I' AND columnD IN (SELECT columnE FROM Table2)
UNION ALL
SELECT COUNT(*) FROM Table
WHERE columnA IN ('B') AND columnB = 'I'
UNION ALL
SELECT COUNT(*) FROM Table
WHERE columnA IN ('R') AND columnB = 'S'
UNION ALL
SELECT COUNT(*) FROM Table
WHERE columnA IN ('A') AND columnB = 'S'
This is the working query and my output is 6 rows, want to maintain that

Answer 1

Let me assume that BI_BRH is unique in STDHOST. This is not strictly necessary but it are simplifying.
Then you can use conditional aggregation. I think putting the values in columns is the simplest approach:
SELECT SUM(CASE WHEN STATUS = 'I' AND TRX_STATE = 'I' AND ASSIGN_TO = '' THEN 1 ELSE 0 END),
SUM(CASE WHEN STATUS = 'I' AND TRX_STATE = 'I' AND ASSIGN_TO <>'' THEN 1 ELSE 0 END)
SUM(CASE WHEN STATUS IN ('A','R') AND TRX_STATE = 'I' AND s.BI_BRH IS NOT NULL THEN 1 ELSE 0 END)
SUM(CASE WHEN STATUS IN ('B') AND TRX_STATE = 'I' THEN 1 ELSE 0 END)
SUM(CASE WHEN STATUS IN ('R') AND TRX_STATE = 'S' THEN 1 ELSE 0 END)
SUM(CASE WHEN STATUS IN ('A') AND TRX_STATE = 'S' THEN 1 ELSE 0 END)
FROM ICSCHQINFO i LEFT JOIN
STDHOST s
ON s.BI_BRH = i.BRH_ASSIGN_TO;

Answer 2

Your code runs 6 times over the same table, with different conditions in the WHERE clause and returns 6 rows.
Assuming that the 6 conditions you have are mutually exclusive, you can create a CTE that returns for each row the category that it belongs to and then aggregate on that category:
WITH cte AS (
SELECT CASE
WHEN STATUS = 'I' AND TRX_STATE = 'I' AND ASSIGN_TO = '' THEN 'cat1'
WHEN STATUS = 'I' AND TRX_STATE = 'I' AND ASSIGN_TO <> '' THEN 'cat2'
WHEN STATUS IN ('A','R') AND TRX_STATE = 'I' AND BRH_ASSIGN_TO IN (SELECT BI_BRH FROM STDHOST) THEN 'cat3'
WHEN STATUS IN ('B') AND TRX_STATE = 'I' THEN 'cat4'
WHEN STATUS IN ('R') AND TRX_STATE = 'S' THEN 'cat5'
WHEN STATUS IN ('A') AND TRX_STATE = 'S' THEN 'cat6'
END category
FROM ICSCHQINFO
)
SELECT category, COUNT(*) counter
FROM cte
GROUP BY category
If there are no rows for any of the categories and in that case you want a row with 0, you need another CTE that returns the categories and LEFT join to the other CTE:
WITH
categories AS (SELECT category FROM (VALUES ('cat1'), ('cat2'), ('cat3'), ('cat4'), ('cat5'), ('cat6')) v(category)),
cte AS (
SELECT CASE
WHEN STATUS = 'I' AND TRX_STATE = 'I' AND ASSIGN_TO = '' THEN 'cat1'
WHEN STATUS = 'I' AND TRX_STATE = 'I' AND ASSIGN_TO <> '' THEN 'cat2'
WHEN STATUS IN ('A','R') AND TRX_STATE = 'I' AND BRH_ASSIGN_TO IN (SELECT BI_BRH FROM STDHOST) THEN 'cat3'
WHEN STATUS IN ('B') AND TRX_STATE = 'I' THEN 'cat4'
WHEN STATUS IN ('R') AND TRX_STATE = 'S' THEN 'cat5'
WHEN STATUS IN ('A') AND TRX_STATE = 'S' THEN 'cat6'
END category
FROM ICSCHQINFO
)
SELECT c.category, COUNT(t.category) counter
FROM categories c LEFT JOIN cte t
ON t.category = c.category
GROUP BY c.category