Thursday, 28 December 2017

The basics of MS SQL (Microsoft SQL Server) & their datatype

The basics of SQL:
What are the difference between DDL, DML and DCL commands?
  1. DDL is Data Definition Language statements. 
    • CREATE - to create objects in the database 
    • ALTER - alters the structure of the database 
    • DROP - delete objects from the database
    • TRUNCATE - remove all records from a table, including all spaces allocated for the records are removed 
    • COMMENT - add comments to the data dictionary 
    • GRANT - gives user's access privileges to database 
    • REVOKE - withdraw access privileges given with the GRANT command
  2. DML is Data Manipulation Language statements. 
    • SELECT - retrieve data from the a database 
    • INSERT - insert data into a table 
    • UPDATE - updates existing data within a table 
    • DELETE - deletes all records from a table, the space for the records remain 
    • CALL - call a PL/SQL or Java subprogram 
    • EXPLAIN PLAN - explain access path to data 
    • LOCK TABLE - control concurrency
  3. DCL is Data Control Language statements.
    • COMMIT - save work done 
    • SAVEPOINT - identify a point in a transaction to which you can later roll back 
    • ROLLBACK - restore database to original since the last COMMIT
    • SET TRANSACTION - Change transaction options like what rollback segment to use

SQL Data Type
  1. Exact numerics
    • bigint 
    • numeric
    • bit
    • smallint
    • decimal
    • smallmoney
    • int
    • tinyint
    • money
  2. Approximate numerics
    • float
    • real
  3. Date and time
      • date
      • datetimeoffset
        • datetime2
        • smalldatetime
        • datetime
        • time
      1. Character strings
        • char
        • varchar
        • text
      2. Unicode character strings
        • nchar
        • nvarchar
        • ntext
      3. Binary strings
        • binary
        • varbinary
        • image
      4. Other data types
        • cursor
        • rowversion
        • hierarchyid
        • uniqueidentifier
        • sql_variant
        • xml
        • Spatial Geometry Types
        • Spatial Geography Types
        • table

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