Commonly used SQL and T-SQL statements (2 ))

-- Data Operations

Select -- retrieve data rows and columns from database tables
Insert -- add new data rows to the database table
Delete -- delete data rows from a database table
Update -- update data in the database table

-- Data Definition

Create Table -- create a database table
Drop table -- delete a table from a database
Alter table -- modify the database table structure
Create View -- create a view
Drop View -- delete a view from a database
Create index -- create an index for the database table
Drop index -- delete an index from a database
Create procedure -- create a stored procedure
Drop procedure -- delete a stored procedure from a database
Create trigger -- create a trigger
Drop trigger -- delete a trigger from a database
Create schema -- Add a new schema to the database
Drop schema -- delete a schema from the database
Create Domain -- create a Data Value Domain
Alter Domain -- change domain definition
Drop Domain -- delete a domain from the database

-- Data Control

Grant -- Grant the user access permission
Deny-Deny User Access
Revoke -- revoke User Access Permissions

-- Transaction control

Commit -- end the current transaction
Rollback -- abort the current transaction
SET transaction -- define the data access features of the current transaction

--ProgramSQL

Declare -- set the cursor for the query
Explain -- describe the data access plan for query
Open -- open a cursor for retrieving query results
Fetch -- retrieve a row of query results
Close -- close the cursor
Prepare -- prepare SQL statements for dynamic execution
Execute -- dynamically Execute SQL statements
Describe -- describe the prepared Query

--- Local variables

Declare @ ID char (10)
-- Set @ ID = '20140901'
Select @ ID = '000000'

--- Global variables

--- It must start @

-- If else

declare @ x int @ Y int @ Z int
select @ x = 1 @ Y = 2 @ z = 3
If @ x> @ Y
Print 'x> y' -- print the string 'x> y'
else if @ Y> @ z
Print 'y> Z'
else print 'z> y'
-- Case
Use pangu
Update employee
set e_wage =
case
when job_level = '1' then e_wage * 1.08
when job_level = '2' then e_wage * 1.07
when job_level = '3' then e_wage * 1.06
else e_wage * 1.05
end
-- while continue break
declare @ x int @ Y int @ C int
select @ x = 1 @ Y = 1
while @ x <3
begin
Print @ X -- print the value of variable x
while @ Y <3
begin
select @ C = 100 * @ x + @ Y
Print @ C -- print the value of variable C
select @ Y = @ Y + 1
end
select @ x = @ x + 1
select @ Y = 1
end
-- waitfor

-- For example, the SELECT statement is executed after 1 hour, 2 minutes, and 3 seconds.

Waitfor delay '01: 02: 03'
Select * from employee

-- For example, the SELECT statement will not be executed until PM.

Waitfor time '23: 08: 00'

Select

Select * (column name) from table_name (Table Name) Where column_name operator value ex host)
Select * From stock_information where stockid = STR (NID)
Stockname = 'str _ name'
Stockname like '% find this %'
Stockname like '[A-Za-Z] %' --------- ([] specifies the range of values)
Stockname like '[^ F-M] %' --------- (^ exclude specified range)
--------- Only wildcard characters can be used in the WHERE clause that uses the like keyword)
Or stockpath = 'stock _ Path'
Or stocknumber: <1000
And stockindex = 24
Not stocksex = 'man'
Stocknumber between 20 and 100
Stocknumber in (10, 20, 30)
Order by stockid DESC (ASC) --------- sort, desc-descending, ASC-ascending
Order by 1, 2 --------- by column number
Stockname = (select stockname from stock_information where stockid = 4)
--------- Subquery
--------- Unless the inner select clause can only return the value of one row
--------- Otherwise, an in qualifier should be used in the outer WHERE clause.
Select distinct column_name form table_name
--------- Distinct: Specifies the unique column value to be retrieved, not repeated.
Select stocknumber, "stocknumber + 10" = stocknumber + 10 from table_name
Select stockname, "stocknumber" = count (*) from table_name group by stockname
--------- Group by groups the table by row. The specified column has the same value.
Having count (*) = 2 --------- having: select the specified group.

Select *
From Table1, Table2
Where table1.id * = table2.id -------- left external connection, which exists in Table1 but not in Table2.
Table1.id = * table2.id -------- right external connection
Select stockname from Table1
Union [all] -------- Union merges the query result set, and all-retains duplicate rows
Select stockname from Table2

Insert

Insert into table_name (stock_name, stock_number) value ("XXX", "XXXX"
Value (select stockname, stocknumber from stock_table2)
------- The value is a SELECT statement.

Update

Update table_name set stockname = "XXX" [where stockid = 3]
Stockname = default
Stockname = NULL
Stocknumber = stockname + 4

Delete

Delete from table_name where stockid = 3
Truncate table_name --------- delete all rows in the table and maintain table integrity
Drop table table_name --------- delete a table completely

Alter table -------- modify Database Table Structure

Alter table database. Owner. table_name add column_name char (2) null ..
Sp_help table_name -------- display existing table features
Create Table table_name (name char (20), age smallint, lname varchar (30 ))
Insert into table_name select -------- delete a column (create a new table)
Alter table table_name drop constraint stockname_default
--------- Delete the default constraint of stockname

 

Common functions)

Conversion functions

Convert (data type, value, Format)

Statistical functions

AVG -- average value
Count -- count
Max -- calculate the maximum value
Min -- Minimum value
Sum -- sum

AVG

Use pangu
Select AVG (e_wage) as dept_avgwage
From employee
Group by dept_id

Max

-- Name of the employee with the highest salary
Use pangu
Select e_name
From employee
Where e_wage =
(Select max (e_wage)
From employee)

STDev ()

-- STDev () function returns the standard deviation of all data in the expression.
-- Stdevp ()
-- The stdevp () function returns the population standard deviation.

VaR ()

-- The VaR () function returns the statistical variation of all values in the expression.

Varp ()

-- Varp () function returns the total number of variations

Arithmetic functions

Trigonometric function

Sin (float_expression) -- returns the sine of the angle in radians
Cos (float_expression) -- returns the cosine of the angle in radians
Tan (float_expression) -- returns the tangent of the angle in radians
Cot (float_expression) -- returns the cotangent of the angle in radians

Inverse trigonometric function

Asin (float_expression) -- returns the angle in radians where the sine is the float value.
ACOs (float_expression) -- returns the angle in radians where the cosine is the float value.
Atan (float_expression) -- returns the angle in radians of the float value.
Atan2 (float_expression1, float_expression2)
------ Returns the radians of float_expression1/float_expres-sion2.
Degrees (numeric_expression)
------ Converts radians to degrees and returns the same data type as the expression.
------ Integer/money/real/Float Type
Radians (numeric_expression)
------ Convert the angle to radians and return the same data type as the expression.

------ Integer/money/real/Float Type
Exp (float_expression) -- returns the exponent value of the expression.
Log (float_expression) -- returns the natural logarithm of the expression.
Log10 (float_expression) -- returns the base-10 logarithm of the expression.
SQRT (float_expression) -- returns the square root of the expression

Approximate value function

Ceiling (numeric_expression)
------- Return> = the minimum integer of the expression. The returned data type is the same as that of the expression.
------- Integer/money/real/Float Type
Floor (numeric_expression)
------- Return the minimum integer of the <= expression. The returned data type is the same as that of the expression.
------- Integer/money/real/Float Type
Round (numeric_expression)
------- Return the data returned by rounding the value with integer_expression as the precision
------- The same type and expression can be integer/money/real/Float Type
ABS (numeric_expression)
------- Return the absolute value of an expression. The returned data type is the same as that of an expression.
------- Integer/money/real/Float Type
Sign (numeric_expression)
------- Positive and negative values of the test parameter return the data type returned by 0 0 0 value 1 positive number or-1 negative number
------- The same as the expression can be of the integer/money/real/Float Type
Pi () ------- the returned value is π, that is, 3.1415926535897936
Rand ([integer_expression])
------- Use the optional [integer_expression] As the seed value to obtain a random floating point number between 0 and 1.

String Functions

ASCII () ------ the function returns the ASCII value of the leftmost character in the character expression
Char () ------ function is used to convert ASCII code to character
------ If no value is entered ~ The Char function returns a null value for the ASCII value between 255.
Lower () ------ function converts all strings to lowercase letters
Upper () ------ function converts all strings to uppercase
STR () ------ function converts numeric data to numeric data
Ltrim () ------ function removes spaces in the string Header
Rtrim () ------ function removes spaces at the end of the string
Left (), right (), substring () -- The function returns some strings.
Charindex (), patindex () -- The function returns the starting position of a specified substring in the string.
Soundex () ------ the function returns a four-digit escape code.
------ The soundex function can be used to search for sound-similar strings. However, the soundex function returns only 0 values for numbers and Chinese characters.
Difference () ------ difference in the two character expressions returned by the soundex Function
------ 0 the first character returned by two soundex functions is different
------ 1 the first character returned by the two soundex functions is the same
------ 2 two soundex functions return the same first and second characters
------ 3 two soundex functions return the same first, second, and third characters.
------ 4 two soundex functions return identical values
Quotename () ------ the function returns a string enclosed by a specific character.

/** // * Select quotename ('abc', '{') quotename ('abc ')
The running result is as follows:

{
{ABC} [ABC] */
Replicate () ------ the function returns a string that repeats character_expression for a specified number of times.
/** // * Select replicate ('abc', 3) replicate ('abc',-2)

The running result is as follows:

Abcabcabc null */
Reverse () ------ the function reverses the character arrangement order of the specified string
Replace () ------ returns the string with the specified substring replaced by the function.
/** // * Select Replace ('abc123g ', '123', 'def ')

The running result is as follows:

Abcdefg */

Space () ------ the function returns a blank string with a specified length.
Stuff () ------ the function uses another substring to replace the substring with the specified position length of the string.

Data Type Conversion Function

The syntax of the cast () function is as follows:
Cast () (as [length])
The convert () function syntax is as follows:
Convert () ([length], [, style])
Select cast (100 + 99 as char) convert (varchar (12), getdate ())

The running result is as follows:
199 Jan 15 2000

Date Functions

Day () ------ function returns the date value in date_expression
Month () ------ function returns the month value in date_expression
Year () ------ function returns the Year Value in date_expression
Dateadd (,,)
----- The function returns the new date generated by the specified date plus the specified additional date interval number.
Datediff (,,)
----- The function returns the datepart differences between two specified dates.

The datename (, ------ function returns the specified part of the date in the form of a string
Datepart (, ------ function returns the specified part of the date in the form of an integer
Getdate () ------ the function returns the current date and time of the system in the default format of datetime.

System Functions

app_name () ------ the function returns the name of the currently executed application.
coalesce () ----- the function returns the value of the first non-null expression among multiple expressions
col_length (<'table _ name'>, <'column _ name'> ---- Length Value of the specified field in the function return table
col_name (, ---- name of the specified field in the function return table, that is, the column name
datalength () ----- the actual length of data returned by the function
db_id (['database _ name']) ------ Number of the database returned by the function
db_name (database_id) ------ name of the database returned by the function
host_id () ----- name of the server computer returned by the function
host_name () ----- the function returns the name of the server computer
identity ([, seed increment]) [as column_name])
-- Identity () the function is only used in the select into statement to insert an identity column to the new table
/**/* Select Identity (INT, 1, 1) as column_name
into newtable
from oldtable */

Isdate () ---- function determines whether the given expression is a reasonable date
Isnull (, -- the function replaces the null value in the expression with the specified value
Isnumeric () ---- the function determines whether the given expression is a reasonable value.
Newid () ---- function returns a value of the uniqueidentifier type.
Nullif (,
---- The nullif function returns the value of xpression1 if expression1 is equal to expression2 and null if not equal.