aggregate functions of SQL for easy understanding of DBMS.pptx

Includes various SQL Aggregate functions

1. 1) COUNT () : Count() function is used to count the number of rows/ tuples in the table. COUNT(*)   or   COUNT( [ALL|DISTINCT] expression )   Syntax : SELECT COUNT( column_name ) FROM  table_name WHERE condition;

2. Count (*):  Returns total number of records . i.e 6. Count(salary):  Return number of Non Null values over the column salary. i.e 5. Count(Distinct Salary):   Return number of distinct Non Null values over the column salary . i.e 4

3. 1) SELECT  COUNT(*)   FROM  PRODUCT_MAST;   Output: 10 2) SELECT  COUNT (*)   FROM  PRODUCT_MAST ;   WHERE  RATE >=20;   Output: 7 3) SELECT COUNT(DISTINCT COMPANY)   FROM PRODUCT_MAST;     Output: 3

4. SELECT  COMPANY , COUNT(*)   FROM  PRODUCT_MAST    GROUP  BY  COMPANY;   Output: Com1 5 Com2 3 Com3 2