Performance tune tSQL Query count(*) & subqueries - tsql

Question

I know that there's a better way to do what I'm trying to accomplish here. Though the query works I fear it's performance will suffer as the dataset's it is applied to grow.
I don't even necesarily need someone to rewrite what I have if they would just be willing to point me in the direction of the topic I should study I would greatly appreciate it.
What I'm trying to return with this query is a count of the number of records at or above a certain status.
Thanks in advance for your help!
SELECT
( SELECT count(*)
FROM TABLE1 c1
WHERE ( c1.U_KEY3 NOT LIKE 'z%' AND (c1.U_KEY1 = '' or c1.U_KEY1 IS NULL) )
) AS 'STATUS is EMPTY'
,
( SELECT count(*)
FROM TABLE1 c1
WHERE ( c1.U_KEY3 NOT LIKE 'z%' AND LEFT(c1.U_KEY1,2) >= '70' )
) AS 'STATUS > 70'
,
( SELECT count(*)
FROM TABLE1 c1
WHERE ( c1.U_KEY3 NOT LIKE 'z%' AND LEFT(c1.U_KEY1,2) >= '50' )
) AS 'STATUS > 50'
,
( SELECT count(*)
FROM TABLE1 c1
WHERE ( c1.U_KEY3 NOT LIKE 'z%' AND LEFT(c1.U_KEY1,2) >= '30' )
) AS 'STATUS > 30'
,
( SELECT count(*)
FROM TABLE1 c1
WHERE ( c1.U_KEY3 NOT LIKE 'z%' AND LEFT(c1.U_KEY1,2) >= '10' )
) AS 'STATUS > 10'

Answer 1

You could roll all the subqueries into a single query using a CASE statement:
SELECT
SUM(CASE WHEN c1.U_KEY1 = '' OR c1.U_KEY1 IS NULL THEN 1 ELSE 0 END) AS 'STATUS IS EMPTY',
SUM(CASE WHEN LEFT(c1.U_KEY1,2) >= '70' THEN 1 ELSE 0 END) AS 'STATUS > 70',
SUM(CASE WHEN LEFT(c1.U_KEY1,2) >= '50' THEN 1 ELSE 0 END) AS 'STATUS > 50',
SUM(CASE WHEN LEFT(c1.U_KEY1,2) >= '30' THEN 1 ELSE 0 END) AS 'STATUS > 30',
SUM(CASE WHEN LEFT(c1.U_KEY1,2) >= '10' THEN 1 ELSE 0 END) AS 'STATUS > 10'
FROM TABLE1 c1
WHERE c1.U_KEY3 NOT LIKE 'z%'
But this might not run as fast as the individual subqueries.

Answer 2

I would turn the question around like this:
DECLARE #t TABLE (Id INT, U_Key1 VARCHAR(4) null);
INSERT INTO #t (id,U_Key1)
VALUES
(1,null),
(2,'902'),
(3,'452'),
(4,'401'),
(5,'103'),
(6,'359'),
(7,'335'),
(8,'772'),
(9,'143'),
(10,'222'),
(11,'664'),
(12,'992'),
(13,'122'),
(14,'332'),
(15,'421'),
(16,'622'),
(17,'982'),
(18,'1234'),
(19,null),
(20,'012');
WITH A AS (
SELECT CAST(LEFT(U_Key1,2) AS INT) val FROM #t
), limits AS (
SELECT 10 limitval, 'Status >= 10' limittext
UNION ALL
SELECT 30 , 'Status >= 30'
UNION ALL
SELECT 50 , 'Status >= 50'
UNION ALL
SELECT 70 , 'Status >= 70'
), Counts AS (
SELECT 'Status is empty' Limittext, COUNT(id) Count FROM #t
WHERE U_Key1 IS null
UNION ALL
SELECT l.limittext, COUNT( A.val) Count FROM A
CROSS JOIN limits l
WHERE A.val >= l.limitval
GROUP BY l.limittext
)
SELECT * FROM Counts
That produces the result:
Status is empty 2
Status >= 10 17
Status >= 30 12
Status >= 50 6
Status >= 70 4