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TABLE CREATION
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CREATE TABLE aggrtable (A INT, B INT);

INSERT INTO aggrtable VALUES(1, NULL);
INSERT INTO aggrtable VALUES(2, NULL);
INSERT INTO aggrtable VALUES(3, NULL);
INSERT INTO aggrtable VALUES(4, NULL);
INSERT INTO aggrtable VALUES(NULL, NULL);
INSERT INTO aggrtable VALUES(1, NULL);
INSERT INTO aggrtable VALUES(2, NULL);
---------------
| A    | B    |
---------------
| 1    | NULL |
| 2    | NULL |
| 3    | NULL |
| 4    | NULL |
| NULL | NULL |
| 1    | NULL |
| 2    | NULL |
---------------
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COUNT
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SELECT COUNT(*) FROM aggrtable;   
SELECT COUNT(ALL *) FROM aggrtable;
7

SELECT COUNT(DISTINCT *) from aggrtable; This syntax is not correct we need to specifically tell the colums where distinct rows are needed.
Invalid


SELECT COUNT(A) FROM aggrtable;
SELECT COUNT(ALL A) FROM aggrtable;
6
SELECT COUNT(DISTINCT A) FROM aggrtable;
4


SELECT COUNT(B) FROM aggrtable;
SELECT COUNT(ALL B) FROM aggrtable;
SELECT COUNT(DISTINCT B) FROM aggrtable;
0


COUNT(*) counts all rows (including those with NULL values), 
COUNT(column_name) counts non-NULL values in a specific column, and
COUNT(DISTINCT column_name) counts distinct non-NULL values.
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SUM
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SELECT SUM(A) FROM aggrtable;
SELECT SUM(ALL A) FROM aggrtable;
13
SELECT SUM(DISTINCT A) FROM aggrtable;
10

SELECT SUM(B) FROM aggrtable;
SELECT SUM(ALL B) FROM aggrtable;
SELECT SUM(DISTINCT B) FROM aggrtable;
NULL

SUM: The SUM function returns the total sum of a numeric column.
SUM(column_name) adds up non-NULL values in a specific column, and 
SUM(DISTINCT column_name) adds up distinct non-NULL values.
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AVG
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SELECT AVG(A) FROM aggrtable;
SELECT AVG(ALL A) FROM aggrtable;
2.1667   (=13/6)

SELECT AVG(DISTINCT A) FROM aggrtable;
2.5000   (=10/4)

SELECT AVG(B) FROM aggrtable;
SELECT AVG(ALL B) FROM aggrtable;
SELECT AVG(DISTINCT B) FROM aggrtable;
NULL
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MAX
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SELECT MAX(A) FROM aggrtable;
SELECT MAX(ALL A) FROM aggrtable;
SELECT MAX(DISTINCT A) FROM aggrtable;
4

SELECT MAX(B) FROM aggrtable;
SELECT MAX(ALL B) FROM aggrtable;
SELECT MAX(DISTINCT B) FROM aggrtable;
NULL
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MIN
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SELECT MIN(A) FROM aggrtable;
SELECT MIN(ALL A) FROM aggrtable;
SELECT MIN(DISTINCT A) FROM aggrtable;
1

SELECT MIN(B) FROM aggrtable;
SELECT MIN(ALL B) FROM aggrtable;
SELECT MIN(DISTINCT B) FROM aggrtable;
NULL

MIN: The MIN function returns the smallest value of the selected column. 
MIN(column_name) finds the minimum non-NULL value in a specific column, and 
MIN(DISTINCT column_name) finds the minimum distinct non-NULL value.
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