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:

INSERT  into VALUES (value 1, value 2,....)

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

INSERT  into 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(<DataValues>)[, (<data values>)] [M...N] | <TableSource> | EXEC <Prodecure> | DEFAULT VALUES}

Example:

Insert  into Values (' USA ')

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

Insert  into  values  ( ' 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:

INSERT  into < table name>[<column list>]<SELECT Statement>

Example:

Declart@MyTable Table(SalesOrderIDint, CustomerIDChar(5)              )INSERT  into @MyTable    SELECTSalesorderid,customerid fromAdventureWorks2008.Sales.SalesOrderHeaderWHERESalesOrderIDbetween 44000  and 44010;

second, UPDATE statement

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

UPDATE SET = WHERE = a value

The complete syntax structure is as follows:

UPDATE [TOP (<expression>)] [PERCENT] <Tabular Object>SET <column> = <Value> [. WRITE (<expression>,<offset>,<length>)][,<column> = <value> [. WRITE (<expression>),<offset>,<length>)]][OUTPUT <source table (s) >][WHERE <restrictive condition>] 　　

BASIC syntax Structure:

UPDATE < table name>SET<column>=< Value>[,<column> = <value>][from< source table (s) >][WHERE <restrictive condition>]

Example:

Update Set = ' China ' where = 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>][WHERE <search condition> | Current of [GLOBAL] <cursorName>]

Its basic grammatical structure is as follows:

DELETE  from
[WHERE= value]

Example:

Delete  from where = 4

SQL statement-Data manipulation