Typical SQL statements

Copy codeThe Code is as follows:
Drop table data TABLE name (permanently delete a data TABLE)

Delete record: delete from table name where condition (rqjs_id = ***)

Update all records: update table name set field name = Value

Conditional update: update table name set field name = value where condition (rqjs_id = ***)

(5) Create and delete data tables:
Create table data TABLE name (Field 1 type 1 (length), Field 2 type 2 (length )...... )
Example: create table tab01 (name varchar (50), datetime default now ())
Drop table data TABLE name (permanently delete a data TABLE)


-- Sentence skill
-- 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
-- Programmatic SQL
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 * from employee

* ** 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 stock *** = '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: Unique column value 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 join, which exists in table1 but not null in table2
Table1.id = * table2.id -------- right external connection

Select stockname from table1
Union [all] ----- union merges query result sets, all-retained 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) --- 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 the database table structure

Alter table database. owner. table_name add column_name char (2)
Null .....
Sp_help table_name ---- display existing features of a table
Create table table_name (name char (20), age smallint, lname
Varchar (30 ))
Insert into table_name select ...... ----- to delete a column (create a new table)
Alter table table_name drop constraint Stockname_default ----
Delete the default constraint of Stockname

* ** Function (/* common functions */)***

---- 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 data of the same type as the expressions.
-- INTEGER/MONEY/REAL/FLOAT Type
RADIANS (numeric_expression) -- converts degrees to RADIANS and returns 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 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) -- returns 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) -- returns the result using integer_expression
Data returned for the precise rounding Value
-- The same type and expression can be INTEGER/MONEY/REAL/FLOAT Type
ABS (numeric_expression) -- returns the absolute value of the expression. The returned data type is the same as that of the expression.
-- INTEGER/MONEY/REAL/FLOAT Type
SIGN (numeric_expression) -- the positive and negative values of the test parameter return the data type returned by 0, zero, 1, positive, or-1 negative.
-- Same as the expression, it can be of the INTEGER, MONEY, REAL, or FLOAT type.
PI () -- the return value is π, that is, 3.1415926535897936
RAND ([integer_expression]) -- use the optional [integer_expression] As the seed value to obtain 0-1.
Random floating point

---- String function ----
ASCII () -- returns the ASCII value of the leftmost character of a character expression.
CHAR () -- function 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 find strings with similar sound. However, the SOUNDEX function returns only 0 values for numbers and Chinese characters.
DIFFERENCE () -- the DIFFERENCE between the two character expressions returned by the SOUNDEX Function
-- 0 the first character returned by the 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 replaces a substring of the specified position length with another substring.

---- Data type conversion function ----
The syntax of the CAST () function is as follows:
CAST () (<expression> AS <data _ type> [length])
The CONVERT () function syntax is as follows:
CONVERT () (<data _ type> [length], <expression> [, style])

Select cast (100 + 99 as char) convert (varchar (12), getdate ())
The running result is as follows:
------------------------------------------
199 Jan 15 2000

---- Date function ----
DAY () -- The function returns the date value in date_expression.
MONTH () -- The function returns the MONTH value in date_expression.
YEAR () -- returns the YEAR Value in date_expression.
DATEADD (<datepart>, <number>, <date>)
-- The function returns the new date generated by the specified date plus the specified additional date interval number.
DATEDIFF (<datepart >,< number >,< date>)
-- The function returns the datepart differences between two specified dates.
DATENAME (<datepart>, <date>) -- The function returns the specified part of the date in the form of a string.
DATEPART (<datepart >,< date>) -- The 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 () -- function returns the name of the currently executed application
COALESCE () -- function returns the value of the first non-NULL expression among multiple expressions.
COL_LENGTH (<'table _ name' >,< 'column _ name'>) -- returns the length value of the specified field in the table.
COL_NAME (<table_id >,< column_id>) -- the name of the specified field in the function return table is the column name.
DATALENGTH () -- the actual length of the 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 () -- The function returns the name of the server computer.
HOST_NAME () -- returns the name of the server computer.
IDENTITY (<data_type> [, seed increment]) [AS column_name])
-- The IDENTITY () function is used only 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 () -- determines whether the given expression is a reasonable date.
ISNULL (<check_expression>, <replacement_value>) -- The function returns NULL in the expression.
Replace the value with the specified value.
ISNUMERIC () -- The function determines whether the given expression is a reasonable value.
NEWID () -- The function returns a value of the UNIQUEIDENTIFIER type.
NULLIF (<expression1>, <expression2>)
-- If the NULLIF function is equal to expression1 and expression2, NULL is returned.
Returns the value of expression1 if the value is not equal.

Reserved Words in SQL

Action add aggregate all
Alter after and
Asc avg avg_row_length auto_increment
Between bigint bit binary
Blob bool both
Cascade case char character
Change check checksum column
Columns comment constraint create
Cross current_date current_time current_timestamp
Data database databases date
Datetime day day_hour day_minute
Day_second dayofmonth dayofweek dayofyear
Dec decimal default delayed
Delay_key_write delete desc describe
Distinct distinctrow double drop
End else escape escaped
Enclosed enum explain exists
Fields file first float
Float4 float8 flush foreign
From for full function
Global grant grants group
Having heap high_priority hour
Hour_minute hour_second hosts identified
Ignore in index infile
Inner insert insert_id int
Integer interval int1 int2
Int3 int4 int8
If is isam join
Key keys kill last_insert_id
Leading left length like
Lines limit load local
Lock logs long longblob
Longtext low_priority max max_rows
Match mediumblob mediumtext mediumint
Middleint min_rows minute minute_second
Modify month monthname myisam
Natural numeric no not
Null on optimize option
Optionally or order outer
Outfile pack_keys partial password
Precision primary procedure process
Processlist privileges read real
References reload regexp rename
Replace restrict returns revoke
Rlike row rows second
Select set show shutdown
Smallint soname SQL _big_tables SQL _big_selects
SQL _low_priority_updates SQL _log_off SQL _log_update
SQL _select_limit
SQL _small_result SQL _big_result SQL _warnings straight_join
Starting status string table
Tables temporary terminated text
Then time timestamp tinyblob
Tinytext tinyint trailing
Type use using unique
Unlock unsigned update usage
Values varchar variables varying
Varbinary with write when
Where year year_month zerofill