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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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