How to Insert or Delete Blank or Null Values in to a SQL Table

SQL DELETE Statement
The DELETE statement is used to delete Rows or Records in a Table.

SQL DELETE Syntax:
DELETE FROM table_name WHERE some_column=some_value

Note: 
Notice the WHERE clause in the DELETE syntax. The WHERE clause specifies which record or records that should be deleted. If you omit the WHERE clause, all records will be deleted!

Example:

Create Table EMPLOYEE
(
EID INT,
EMPNAME VARCHAR(25) , 
DEPT VARCHAR(25),
DOJ DATE , 
SAL DECIMAL(7,2)
)

GO

Entering Records with Null or Blank Values :

INSERT INTO EMPLOYEE 
SELECT 123,'REDDY','TECH','02-20-2014',25450.25 UNION ALL
SELECT 234,'RAMYA','PROD','03-20-2014',35450.25 UNION ALL

SELECT '','RAJU','MARKETING','04-20-2014',45450.25 UNION ALL 'EID as Blank Value
SELECT NULL,'KAJAL','CRM','04-20-2014',55450.25 UNION ALL 'EID as NULL Value
SELECT 456,'SRUTHI','','05-20-2014',65450.25 'DEPT as BlankValue

GO

EID	EMPNAME	DEPT	DOJ	SAL
123	REDDY	TECH	2/20/2014	25450.25
234	RAMYA	PROD	3/20/2014	35450.25
0	RAJU	MARKETING	4/20/2014	45450.25
NULL	KAJAL	CRM	4/20/2014	55450.25
456	SRUTHI		5/20/2014	65450.25

Deleting Records with Null or Blank Values :

DELETE FROM EMPLOYEE WHERE  EID = '' OR EID IS NULL OR DEPT=''

Note :
When you pass Blank value to a Numeric Field , it will take '0' as Value.
When you pass Blank value to a Text Field , it will take '' as Value.
To delete a record with NULL value , we have to use IS NULL condition. No Logical operator can be applicable.

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