WHERE clause in PostgreSQL

PostgreSQL WHERE
The PostgreSQL WHERE clause is used with SELECT, INSERT, UPDATE and DELETE statements to return the result only when the condition is satisfied.

Syntax:

WHERE conditions; 

Example 1: Selecting specific fields from a table.
Employment table:

ID STATE RATE
1 A 60
2 B 70
3 C 65
4 D 80
5 E 78

Query:

SELECT *  
FROM “EMPLOYMENT”
WHERE  “RATE” > 60;

Output:

ID STATE RATE
2 B 70
3 C 65
4 D 80
5 E 78

Example 2: Using WHERE clause with AND condition.
Employment table:

ID STATE RATE
1 A 60
2 B 70
3 C 65
4 D 80
5 E 78

Query:

SELECT *  
FROM “EMPLOYMENT”
WHERE  “RATE” > 60
AND “ID” < 4;

Output:

ID STATE RATE
2 B 70
3 C 65

Example 3: Using WHERE clause with OR condition.
Employment table:

ID STATE RATE
1 A 60
2 B 70
3 C 65
4 D 80
5 E 78

Query:

SELECT *  
FROM “EMPLOYMENT”
WHERE  “RATE” > 60
OR “ID” < 4;

Output:

ID STATE RATE
1 A 60
2 B 70
3 C 65
4 D 80
5 E 78

Example 4: Using WHERE clause with both AND and OR condition.
Employment table:

ID STATE RATE
1 A 60
2 B 70
3 C 65
4 D 80
5 E 78

Query:

SELECT *  
FROM “EMPLOYMENT”
WHERE  (“RATE” > 60 AND “STATE” = ‘C’)
OR “ID” > 4;

Output:

ID STATE RATE
3 C 65
5 E 78
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