Oracle SQL Tutorial Contents

You can filter information using where conditions like suppose you want to see only those employees whose salary is above 5000 then you can type the following query with where condition

SQL>select * from emp where sal > 5000;

To see those employees whose salary is less than 5000 then the query will be

SQL> select * from emp where sal < 5000;

Logical Conditions

A logical condition combines the results of two component conditions to produce a single result based on them or to invert the result of a single condition. Table below lists logical conditions.

Condition	Operation	Example
NOT	Returns TRUE if the following condition is FALSE. Returns FALSE if it is TRUE. If it is UNKNOWN, it remains UNKNOWN.	SELECT * FROM emp WHERE NOT (sal IS NULL); SELECT * FROM emp WHERE NOT (salary BETWEEN 1000 AND 2000);
AND	Returns TRUE if both component conditions are TRUE. Returns FALSE if either is FALSE. Otherwise returns UNKNOWN.	SELECT * FROM employees WHERE ename ='SAMI' AND sal=3000;
OR	Returns TRUE if either component condition is TRUE. Returns FALSE if both are FALSE. Otherwise returns UNKNOWN.	SELECT * FROM emp WHERE ename = 'SAMI' OR sal >= 1000;

Membership Conditions

A membership condition tests for membership in a list or subquery

The following table lists the membership conditions.

Condition	Operation	Example
IN	"Equal to any member of" test. Equivalent to "= ANY".	SELECT * FROM emp WHERE deptno IN (10,20); SELECT * FROM emp WHERE deptno IN (SELECT deptno FROM dept WHERE city=’HYD’)
NOT IN	Equivalent to "!=ALL". Evaluates to FALSE if any member of the set is NULL.	SELECT * FROM emp WHERE ename NOT IN ('SCOTT', 'SMITH');

Null Conditions

A NULL condition tests for nulls.

What is null?

If a column is empty or no value has been inserted in it then it is called null. Remember 0 is not null and blank string ‘ ’ is also not null.

The following example lists the null conditions.

Condition

Operation

Example

IS [NOT]

NULL

Tests for nulls. This is the only condition that you should use to test for nulls.

SELECT ename FROM emp WHERE deptno IS NULL;

SELECT * FROM emp WHERE ename IS NOT NULL;

EXISTS Conditions

An EXISTS condition tests for existence of rows in a subquery.

The following example shows the EXISTS condition.

Condition	Operation	Example
EXISTS	TRUE if a subquery returns at least one row.	SELECT deptno FROM dept d WHERE EXISTS (SELECT * FROM emp e WHERE d.deptno = e.deptno);

Condition

Operation

Example

EXISTS

TRUE if a subquery returns at least one row.

SELECT deptno FROM dept d WHERE EXISTS
(SELECT * FROM emp e
WHERE d.deptno = e.deptno);

LIKE Conditions

The LIKE conditions specify a test involving pattern matching. Whereas the equality operator (=) exactly matches one character value to another, the LIKE conditions match a portion of one character value to another by searching the first value for the pattern specified by the second. LIKE calculates strings using characters as defined by the input character set.

For example you want to see all employees whose name starts with S char. Then you can use LIKE condition as follows

SQL> select * from emp where ename like ‘S%’ ;

Similarly you want to see all employees whose name ends with “d”

SQL>select * from emp where ename like ‘%d’;

You want to see all employees whose name starts with ‘A’ and ends with ‘d’ like ‘Abid’, ’Alfred’, ’Arnold’.

SQL>select * from emp where ename like ‘A%d’;

You want to see those employees whose name contains character ‘a’ anywhere in the string.

SQL> select * from emp where ename like ‘%a%’;

To see those employees whose name contains ‘a’ in second position.

SQL>select * from emp where ename like ‘_a%’;

To see those employees whose name contains ‘a’ as last second character.

SQL>select * from emp where ename like ‘%a_’;

To see those employees whose name contain ‘%’ sign. i.e. ‘%’ sign has to be used as literal not as wild char.

SQL> select * from emp where ename like ‘%\%%’ escape ‘\’;