Creation and modification of basic tables and data in them by SQL statements of SQL Server

SQL Statement to create a basic table

create table  { <  Table name > |  Database name . [ dbo . ]  Table name }

(

        Name   data type    [ Column level integrity constraints ]  

       [ ,  Name   data type    [ Column level integrity constraints ]  ]

       ......

       [  Table level integrity constraints ]

)

【 Column level constraints 】 It refers to adding  primary key （ Primary key constraint ）、unique（ Uniqueness constraint ） or  NULL、NOT NULL  or identity（seed,increment）（ Identity column ）、default  expression （ Specify default ）.

【 Table level constraints 】 It means adding  primary key ( Name , Name . . . ) （ Specify multiple columns as primary keys ）、foreign key(  Foreign key column name ) references  Main table ( Name ) （ Create foreign key constraints ）.

Another is to create a temporary table ：

create table #  Table name

. . . . . .

“#” Represents a temporary local table , Use in the current database , Delete when the current database is closed ;“##” Represents a global temporary table , It can be used in all databases , After closing all databases, delete .

SQL Statement to modify the basic table

Alter Table <  Table name >

[  Alter column  < Old column names > 

        New column names | New data types | [NULL | NOT NULL] 

] 

[  Add  [column] < New column names >  <  data type >  [ Integrity constraints ]  ]    -- Add column

[  Add  < Table level integrity constraints >  ]  [ , . . . n ]

[ Drop [column]  < Name >  [cascade | restrict]  ]    -- Delete a column , If added cascade It means that other columns that reference this column will also be deleted , If added restrict, If the column is referenced by other objects , This column will not be deleted .

[ Drop  constraint  < Integrity constraint name ( Name )>  ] -- Delete the integrity constraint of a column  

Delete base table

Drop Table < Table name > [  cascade | restrict ]       -- If added cascade When deleting the basic table, the related dependent objects will also be deleted , If added restrict, If there are objects that depend on this table , This table will not be deleted .

Maintenance of data in the table

insert data

insert  < Table name >

[ ( Name , Name ,. . . ) ]

values (' data ',' data ',. . .)   [ , ( '  data ', . . . ) ]

Column names and data are one-to-one correspondence , If no column name is specified , Sort by default column name

Modifying data

update  Table name

set 

          Name =  The new value   [ , . . . n]    --  This column will be changed to the new value

         [ from  Other table names [, . . .n]   ]     -- Specify that the data to be updated will come from other tables

         [ where  Conditions ]       -- Restrict the rows to be updated by constraints , Instead of updating every row of data

Truncate Table  Table name     -- All rows in the table will be deleted , And the deletion of each line will not be included in the log file , In this way, the speed will be faster , in addition , The structure of the table 、 Column 、 constraint 、 Index and so on remain unchanged