Selecting values from the database table


Select query is used to select data from database table. The syntax is below:
Syntax:- Select column_name from table_name.
Use distinct keyword if you want to return only distinct (not common) values.
Syntax:- select distinct column_name from table_name
Sorting Rows:


Order by clause is used to return result in sorted way. For example:


Select column_name from table_name order by column_name


Joins:
Inner Join, Left Join, Right Join, Union Join


Inner Join:
Return all the rows matching in both the tables.


Left Join:
Return all the rows of first table even if they are not matching with second table.


Right Join:
Return all the rows of second table even if they are not matching with first table.


Union:
To display information from two tables with same data type. Union ALL will display duplicate rows of two tables.


Difference between truncate and delete:


Truncate will remove all the data from a table but it will not delete the table itself.


ALTER TABLE:
This statement is used to add or drop columns in an existing table.