Shulou(Shulou.com)06/01 Report--

Data type

Exact number

Approximate number

String

Unicode string

**

1. Create a tabl

Create table table name (column name 1 data type (size), column name 2 data type (size) column name 3 data type (size))

Delete tabl

Drop table

Add column

ALTER TABLE table name

ALTER COLUMN column name data type (size)

Column: alter table www add remarks nvarchar (10)

# add a comment column to the www table

* * modify the data type of the column * * ALTER TABLE table name

ALTER COLUMN column name data type (size)

Column: alter table www alter column remarks nvarchar (1000)

# modify the 'remarks' column data type length to 1000 in the www table

Delete column

ALTER TABLE table name

DROP COLUMN column name

Column: alter table www drop column comment

# delete the "remarks" table name from the www table

Insert data

INSERT [INTO] [column name] VALUES

Column: insert into www values ('10-10-11 'tomatoes,' vegetables', '2.1-10-11')

# add a column of data to the www table

Update data

UPDATE SET [WHERE]

Set can be followed by the values of multiple data columns, and no one where can be used to restrict conditions.

Column: update www set sales Price = 1000 where name = 'Apple'

The sales price of # www update is 1000, effective only for those whose name is Apple.

Delete data

1.delete delete statement

DELETE FROM [WHERE]

Column: delete from www where name = 'Apple'

# Delete the data named Apple in the www table

2.Truncate Table statement

The Truncate Table statement can only be used to delete the contents of the entire table

Column: Truncate table www

# Delete everything in the www table

Data query

Conditional expression

Comparison operator

Wildcard character

Logical operator

Select from www | query www table

Select name, title, base salary from www | query in www table only shows name, position and base salary.

Select name from www where Job = 'Finance Department' | query job in www table = employee of Finance Department

Select from www where salary betweer 8000 and 10000 | query the information of employees with www salary ranging from 8000 to 10000.

Select from www where salary 20000 | query the information of employees with less than 10000 or more than 20000 in www table

Select from www where salary in (8000,9000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000) |

Select from www where name like 'Zhang%' | query employee information whose names begin with Zhang in the www table

Select from www where name like 'Yang%' and Job = 'Finance Department' | query www surname Yang and is an employee of Finance Department

Select from www where hobby is not null | query the information of employees whose hobbies are empty in the www table.

Select top 5 from www | query the first five lines of data in www

Select name as name, sales location as xxx, sales price as ddd from sales | set alias

Select * from www order by basic salary desc | query the employee information of www table and display it from high to low

Select distinct Job from www | query which jobs are in the www table and remove duplicates

Select name, title, gender into new1 from www | query the name, title and gender in the www table, and check it in the new table.

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