SQL statement-Data manipulation

SQL statement-Data manipulation

Changes in the data in the table are reaching, which can also result in changes to the data in the index. Therefore, if the query statement does not require an index, you should delete the useless index to improve efficiency.

One, insert statement

　　1. Basic INSERT statement

Insert is used to enter data into a table with the following syntax structure:

Values (value 1, value 2,....)

We can also specify the columns for which you want to insert data:

Values (value 1, value 2,....)

The entire syntax structure is as follows:

 　　 INSERT[TOP (<expression>) [PERCENT] ][Into]<tabular Object>[(<column list>)][OUTPUT <output clause>] {values (<data values[m...n | <table source> Span style= "color: #808080;" >| exec <prodecure| default values}        

Example:

VALUES (' America ')  

A new feature was added in SQL Server2008, allowing multiple lines to be inserted at once, separated by commas "," such as:

intovalues (' America '), (' UK ');       

　　2. INSERT into ... SELECT statement

What to do when we need to use some data sources as insert data. Data sources such as:

• Another table in the database
• A completely different database on the same server
• A class of queries or other data from another SQL Server
• Same table

INSERT into ... The SELECT statement completes the ability to insert a block of data at a time. Its syntax structure is a combination of the INSERT statement and the SELECT statement syntax structure:

<table name>[<column list>]<SELECT statement>  

Example:

Declart@MyTabletable (SalesOrderID char (5insert into  @MyTable select Salesorderid,customerid from AdventureWorks2008.Sales.SalesOrderHeader  WHERE SalesOrderID between 44000 Span style= "color: #808080;" >and 44010;         

second, UPDATE statement

The UPDATE statement updates the data in the table with the simplest syntax structure:

= a value

The complete syntax structure is as follows:

UPDATE[TOP (<expression>)][PERCENT]<tabular Object>SET<Column> = <value> [[,<column> = <value> [. WRITE (<expression>),<offset>,<length>) ][output <source Table (s) >][where <restrictive condition>                 

BASIC syntax Structure:

<table name><column<value[,<column> = <value>][ From <source table (s) >][WHERE <restrictive condition>]   

Example:

' China 4 

Third, DELETE statement

The DELETE statement is used to delete data from the table, and the complete syntax structure of the DELETE statement is as follows:

DELETE[top (<expression>) [Percent] [from <tabular object>[ OUTPUT <output clause> ][from <table or Join Condition>][< cursor name>]       

Its basic grammatical structure is as follows:

From table name  [= value]

Example:

4

SQL statement-Data manipulation