Select statement can perform two types of job Selection Projection  Column wise projection Row wise projection Selection It means select all data from table and not apply any clause. Ex: SELECT * FROM student; Projection - Column wise Projection Column restriction is a concept through which those many attributes are displayed which are mentioned in the select statement Ex: SELECT Name, Mobile FROM student; Projection - Row wise Projection Row restriction is a concept through which those many records are displayed where condition is satisfied. Ex: SELECT Name, Mobile FROM student WHERE ID = 5; Column Alias Column alias is concept through which user can provide duplicate name to an existing column. It can be given using three different methods Type-1 SELECT Name Name, Mobile Mobile FROM student; Type-2 SELECT Name 'Name', Mobile 'Name' FROM student; Type-3 SELECT Name as 'Student Name', Mobile as 'Mobile Name' FROM student; Column Concatenation Column

Select <exp> From <t_name> [where<cond>] [group<col_name>] [having by <group col_name>] [order by <col_name>[asc|desc]];

 “It is a concept or a mech. Implemented on select statement to extract data from multiple tables.” To extract date from multiple tables the table must have a relation and depending on the relation join is categories in 4 diff types. 1.             Equijoin 2.             Non equijoin 3.             Self or inner join 4.             Outer join EQUI JOIN:         It is a type of join which will extract date from multiple tables won is available. Emp                                                                                          Emp no      Name        Sal       Dept no         Xid          1         X         2300         20         X1         2         Y         2500         10         X2         3         Z         3600         20         X3         4         Aa               9300         30         X4         5         Bb         6300         10         X5 Dept       Dept no        Dname          Loc

“ Constraint is rule or restriction imposed and individual column to above data enter “ Oracle provide the following constraint to do so 1.      Primary key 2.      Not Null 3.      Unique 4.      Check 5.      Foreign Key 1.     PRIMARY KEY:        This is constraint which in forces not null value and no report value in a column using this constraint the record is unique identify. 2.     NOT NULL        This is constraint no not null value is column but it accepts duplicate value. 3.     UNIQUE        Using this constraint no duplicate value is allow in column but accepts null 4.     CHECK        It is used for check a condition. NOTE:        Multiple value null value accept in column the column                      5.     FOREGIN KEY        This is constraints which helpful up to make relationship between two or more than two table using a common attribute. It always refers to same table primary key or another table primary key to make a relationship. It is just opposite of primary