WHERE clause used into PostgreSQL statement to specify/apply any condition while retrieving, updating or deleting data from a table.
Syntax: PostgreSQL statement using WHERE clause
PostgreSQL WHERE clause example
Insert some records on above table ("Employee")
Illustrates of WHERE clause
Syntax: PostgreSQL statement using WHERE clause
SELECT <Column Name1>,<Column Name2>... FROM table_name WHERE <condition>; |
The following table illustrates the standard comparison operators.
Operator Description
= Equal
> Greater than
< Less than
>= Greater than or equal
<= Less than or equal
<> or != Not equal
AND Logical operator AND
OR Logical operator OR
PostgreSQL WHERE clause example
Suppose we have a table "Employee" so first we create a table using the following query.
CREATE TABLE public."Employee" ( "Id" bigserial NOT NULL, "FName" text COLLATE pg_catalog."default", "LName" text COLLATE pg_catalog."default", "UserName" text COLLATE pg_catalog."default", "Password" text COLLATE pg_catalog."default", "Contact" text COLLATE pg_catalog."default", "Salary" numeric NOT NULL DEFAULT 0.0, CONSTRAINT "PK_Test" PRIMARY KEY ("Id") ) |
Insert some records on above table ("Employee")
INSERT INTO public."Employee"( "FName", "LName", "UserName", "Password", "Contact", "Salary") VALUES ('Name1','last1', 'name1@gmail.com', 'name@0123', '9088877787', '20000'); INSERT INTO public."Employee"( "FName", "LName", "UserName", "Password", "Contact", "Salary") VALUES ('Name2','last2', 'name2@gmail.com', 'name@0123', '9288877787', '30000'); INSERT INTO public."Employee"( "FName", "LName", "UserName", "Password", "Contact", "Salary") VALUES ('Name3','last3', 'name3@gmail.com', 'name@0123', '9388877787', '40000'); |
Illustrates of WHERE clause
1- Used WHERE clause when selecting a particular record(s) Query: If you want to select the user which UserName and Password are name1@gmail.com and name@0123
SELECT "Id", "FName", "LName", "UserName", "Password", "Contact", "Salary" FROM public."Employee" WHERE "UserName"='name1@gmail.com' AND "Password"='name@0123' |
2- Used WHERE clause when updating particular record: Suppose you want to update Salary of employee Name2 then use the below statement
UPDATE public."Employee" SET "Salary"=50000 WHERE "UserName"='name2@gmail.com' AND "Password"='name@0123' |
3- Used WHERE clause when deleting a particular record(s): Suppose you want to delete 3rd-row record (I am deleting record using Id)
DELETE FROM public."Employee" WHERE "Id" = 3; |