Here I am posting some simple SQL commands. My intention is not to introduce SQL commands to the reader or make her an expert. I know these clauses are so simple & easy to remember but still I made this post so that you can do a quick revision before attending an interview.
Select command
For specifying the data which need to be displayed from a table.
Syntax:
SELECT * from tablename
SELECT columnname1, columnname2, … FROM tablename
Select command
For specifying the data which need to be displayed from a table.
Syntax:
SELECT * from tablename
SELECT columnname1, columnname2, … FROM tablename
SELECT DISTINCT Statement
For displaying distinct values within the selection.
Syntax:
SELECT DISTINCT colunmnname FROM tablename
SELECT with WHERE
For selecting some values from a table satisfying a particular condition
Syntax:
SELECT colunmnname FROM tablename WHERE {condition}
Some examples where different conditions are used in combination with SELECT.
SELECT colunmnname FROM tablename WHERE columnname1=‘value1’ AND Columnname2=’value2’
SELECT colunmnname FROM tablename WHERE columnname1=‘value1’ OR columnname2=’value2’
SELECT colunmnname FROM tablename WHERE columnname1=‘value1’ AND (columnname2=’value2’ OR columnname2=’value3’)
INSERT statement
To insert data into a table.
Syntax:
INSERT INTO tablename (columnname1, columnname2, …) VALUES (‘value1’, ‘value2’, …)
Delete From statement
To remove some elements from a table.
Syntax:
DELETE FROM tablename WHERE {condition}
Update Statement
To change the value of an element in the table. Where condition can be used with it.
Syntax:
UPDATE tablename SET columnname1 = [new_value1], Columnname1 = [new_value2] WHERE {condition}