SQL – Data Types

SQL – Data Types

SQL data type is an attribute that specifies type of data of any object. Each column, variable and expression has related data type in SQL.
You would use these data types while creating your tables. You would choose a particular data type for a table column based on your requirement.
SQL Server offers six categories of data types for your use:

Exact Numeric Data Types:

DATA TYPE	FROM	To
bigint	-9,223,372,036,854,775,808	9,223,372,036,854,775,807
int	-2,147,483,648	2,147,483,647
smallint	-32,768	32,767
tinyint	0	255
bit	0	1
decimal	-10^38 +1	10^38 .1
numeric	-10^38 +1	10^38 .1
money	-922,337,203,685,477.5808	+922,337,203,685,477.5807
smallmoney	-214,748.3648	+214,748.3647

Approximate Numeric Data Types:

DATA TYPE	FROM	To
float	-1.79E + 308	1.79E + 308
real	-3.40E + 38	3.40E + 38

Date and Time Data Types:

DATA TYPE	FROM	To
datetime	Jan 1, 1753	Dec 31, 9999
smalldatetime	Jan 1, 1900	Jun 6, 2079
date	Stores a date like June 30, 1991
time	Stores a time of day like 12:30 P.M.

Note: Here datetime has 3.33 milliseconds accuracy where as smalldatetime has 1 minute accuracy.

Character Strings Data Types:

DATA TYPE	FROM	To
Char	char	Maximum length of 8,000 characters.( Fixed length non-Unicode characters)
Varchar	varchar	Maximum of 8,000 characters.(Variable-length non-Unicode data).
varchar(max)	varchar(max)	Maximum length of 231characters, Variable-length non-Unicode data (SQL Server 2005 only).
Text	text	Variable-length non-Unicode data with a maximum length of 2,147,483,647 characters.

Unicode Character Strings Data Types:

DATA TYPE	Description
nchar	Maximum length of 4,000 characters.( Fixed length Unicode)
nvarchar	Maximum length of 4,000 characters.(Variable length Unicode)
nvarchar(max)	Maximum length of 231characters (SQL Server 2005 only).( Variable length Unicode)
ntext	Maximum length of 1,073,741,823 characters. ( Variable length Unicode )

Binary Data Types:

DATA TYPE	Description
binary	Maximum length of 8,000 bytes(Fixed-length binary data )
varbinary	Maximum length of 8,000 bytes.(Variable length binary data)
varbinary(max)	Maximum length of 231 bytes (SQL Server 2005 only). ( Variable length Binary data)
image	Maximum length of 2,147,483,647 bytes. ( Variable length Binary Data)

Misc Data Types:

DATA TYPE	Description
sql_variant	Stores values of various SQL Server-supported data types, except text, ntext, and timestamp.
timestamp	Stores a database-wide unique number that gets updated every time a row gets updated
uniqueidentifier	Stores a globally unique identifier (GUID)
xml	Stores XML data. You can store xml instances in a column or a variable (SQL Server 2005 only).
cursor	Reference to a cursor object
table	Stores a result set for later processing

SQL - Syntax

SQL – Syntax

SQL is followed by unique set of rules and guidelines called Syntax. This tutorial gives you a quick start with SQL by listing all the basic SQL Syntax:
All the SQL statements start with any of the keywords like SELECT, INSERT, UPDATE, DELETE, ALTER, DROP, CREATE, USE, SHOW and all the statements end with a semicolon (;).
Important point to be noted is that SQL is case insensitive which means SELECT and select have same meaning in SQL statements but MySQL make difference in table names. So if you are working with MySQL then you need to give table names as they exist in the database.

SQL SELECT Statement:

SELECT column1, column2....columnN

FROM   table_name;

SQL DISTINCT Clause:

SELECT DISTINCT column1, column2....columnN

FROM   table_name;

SQL WHERE Clause:

SELECT column1, column2....columnN

FROM   table_name

WHERE  CONDITION;

SQL AND/OR Clause:

SELECT column1, column2....columnN

FROM   table_name

WHERE  CONDITION-1 {AND|OR} CONDITION-2;

SQL IN Clause:

SELECT column1, column2....columnN

FROM   table_name

WHERE  column_name IN (val-1, val-2,...val-N);

SQL BETWEEN Clause:

SELECT column1, column2....columnN

FROM   table_name

WHERE  column_name BETWEEN val-1 AND val-2;

SQL Like Clause:

SELECT column1, column2....columnN

FROM   table_name

WHERE  column_name LIKE { PATTERN };

SQL ORDER BY Clause:

SELECT column1, column2....columnN

FROM   table_name

WHERE  CONDITION

ORDER BY column_name {ASC|DESC};

SQL GROUP BY Clause:

SELECT SUM(column_name)

FROM   table_name

WHERE  CONDITION

GROUP BY column_name;

SQL COUNT Clause:

SELECT COUNT(column_name)

FROM   table_name

WHERE  CONDITION;

SQL HAVING Clause:

SELECT SUM(column_name)

FROM   table_name

WHERE  CONDITION

GROUP BY column_name

HAVING (arithematic function condition);

SQL CREATE TABLE Statement:

CREATE TABLE table_name(

column1 datatype,

column2 datatype,

column3 datatype,

.....

columnN datatype,

PRIMARY KEY( one or more columns )

);

SQL DROP TABLE Statement:

DROP TABLE table_name;

SQL CREATE INDEX Statement :

CREATE UNIQUE INDEX index_name

ON table_name ( column1, column2,...columnN);

SQL DROP INDEX Statement :

ALTER TABLE table_name

DROP INDEX index_name;

SQL DESC Statement :

DESC table_name;

SQL TRUNCATE TABLE Statement:

TRUNCATE TABLE table_name;

SQL ALTER TABLE Statement:

ALTER TABLE table_name {ADD|DROP|MODIFY} column_name {data_ype};

SQL ALTER TABLE Statement (Rename) :

ALTER TABLE table_name RENAME TO new_table_name;

SQL INSERT INTO Statement:

INSERT INTO table_name( column1, column2....columnN)

VALUES ( value1, value2....valueN);

SQL UPDATE Statement:

UPDATE table_name

SET column1 = value1, column2 = value2....columnN=valueN

[ WHERE  CONDITION ];

SQL DELETE Statement:

DELETE FROM table_name

WHERE  {CONDITION};

SQL CREATE DATABASE Statement:

CREATE DATABASE database_name;

SQL DROP DATABASE Statement:

DROP DATABASE database_name;

SQL USE Statement:

USE DATABASE database_name;

SQL COMMIT Statement:

COMMIT;

SQL ROLLBACK Statement:

ROLLBACK;