DBMS SQL Queries

Command: Create

Purpose: This command is used to create tables.

Syntax: Create table <table name> (column 1 data type<size>, column 2 data type <size>);

Example::SQL> create table student2(s_no varchar2(4), name char(15), roll_no varchar2(6), branch char(10));
 

Command: Desc

Purpose: This command is used to describe table.

Syntax: desc <table name>;

Example::
SQL> desc student2;
Name Null? Type
  Command: Insert

Purpose: This command inserts values in the table.

Syntax: Insert into table name (col name 1, column name 2) values (value1, value2);

Example::
SQL> insert into student2 values (1,'AMAN', 7213,'c.s.e.');

SQL> insert into student2 values (2,'ANKIT’, 7216,'c.s.e.');

SQL> insert into student2 (s_no,name,branch) values(3,' ADITYA',7206,'c.s.e.');
  Command: Select

Purpose: Selects all columns and rows from table,* and distinct are the options used with it.

Syntax: Select [distinct] <tablename.columnname>
From<tablename>
[Where <condition>]
[Group by<columnname(s)>]
[Having <condition>]
[Order by <expression>];

Example::
SQL> select * from student2;

SQL> select * from student2 where name='ANKIT';

SQL> select * from student2 where s_no=3;
  Command: Alter

Purpose: This is used to modify the structure of the table.

Syntax: Alter table name add<new column datatype<size>;

Example::
SQL> alter table student2 add( address varchar2(25));

SQL> select * from student2;

SQL> alter table student2 modify( address varchar(28));

SQL> alter table student2 drop(address);

SQL> select * from student2;
  Command: Delete

Purpose: This command is used to delete all the rows or either a set of rows from a table.

Syntax: Delete from <table name>;
Delete from <table name> where <condition>;

Example::
SQL> delete from student2 where name='purneet';

SQL> select * from student2;

SQL> delete from student2;

SQL> select * from student2;
  Command: Update

Purpose: This command is used to change and modify the data values in a table.

Syntax:Update <table name>set<column name1>=<expresson1>, < column name2>=<expresson2>;

Example::
SQL> update student2 set name='AKSHAY' where s_no=3;

SQL> select * from student2;
  Command: Rename

Purpose: This command is used to rename a table.

Syntax: Rename<table name> to <new table name>;

Example::
SQL>rename student2 to student;

SQL> select * from student;
  Command: Order by command

Purpose: The ORDER BY clause sorts the result set based on the columns specified.

Syntax: Order by<column name1>, <column name2> <[sort order]>;

Example::
SQL> select * from student2 order by roll_no asc;

SQL> select * from student2 order by s_no asc;

SQL> select * from student2 order by s_no desc;
  Command: Drop

Purpose: This command is used to destroy a table.

Syntax: Drop table <table name>;

Example::
SQL> drop table student2;

SQL> select * from student2;

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