Showing posts with label SQL. Show all posts
Showing posts with label SQL. Show all posts

Thursday, January 7, 2016

What is SQL?


Structured Query Language.
  •  T-SQL language 
  • Getting information from the database using the SELECT statement.
  • Fetching Data
  • Transact-SQL (T-SQL) language 

SQL is a standard language for accessing databases.
 SELECT statement
  • SELECT
  • FROM
  • WHERE
  • ORDER BY

SQL Statements: DDL, DML and DCL:

  1. Data Definition Language (DDL)
  2. Data Manipulation Language (DML) 
  3. Data Control Language (DCL) 
  4. Transaction Control (TCL) 

Monday, August 3, 2015

What is the full form of mdf, ldf and ndf in SQL Server?

SQL Server databases have three types of files:

Primary data files
The primary data file is the starting point of the database and points to the other files in the database. Every database has one primary data file. The recommended file name extension for primary data files is .mdf.

Secondary data files
Secondary data files comprise all of the data files other than the primary data file. Some databases may not have any secondary data files, while others have multiple secondary data files. The recommended file name extension for secondary data files is .ndf.

Log files
Log files hold all of the log information used to recover the database. There must be at least one log file for each database, although there can be more than one. The recommended file name extension for log files is .ldf.

SQL Server does not enforce the .mdf, .ndf, and .ldf file name extensions, but these extensions are recommended to help identify the use of the file.