group by name

Count Group function: (filter out fields that are empty)Select count (Address), COUNT (*) from B_userMax () Avg () min (), SUM ()Select SUM (age), Max (age), min (age), Avg (NVL (age,0)) from B_user1 260 70) 10 37.1428571428571groupby: If the field

Find duplicate data in MySQL, delete duplicate data create table and test data * Table Structure * DROPTABLEIFEXISTS 't1'; CREATETABLEIFNOTEXISTS 't1' ('id' INT (1) NOTNULLAUTO_INCREMENT, 'name' VARCHAR (20) NOTNULL, 'add' VARCHAR (20) NOTNULL,

For example: ID name value 1 A PP 2 A PP 3 B III 4 B PP 5 B PP 6 c pp 7 c pp 8 C III ID is the primary key This result is required. ID name value 1 A PP 3 B III 4 B PP 6 c pp 8 C III Method 1 Delete yourtable Where [ID] Not in ( Select max ([ID])

For example: Id name value 1 a pp 2 a pp 3 B iii 4 B pp 5 B pp 6 c pp 7 c pp 8 c iii Id is the primary key This result is required. Id name value 1 a pp 3 B iii 4 B pp 6 c pp 8 c iii Method 1 Delete YourTable Where [id] not in ( Select max ([id])

You can use the aggregate function count (*) in Mysql to implement this function. For example, to query the records with the most frequently displayed names in the user table, you can group the records by group by name first, use count to calculate

For example, if the primary key is required to obtain such results as idnamevalue1app3biii4bpp6cpp8ciii method 1 deleteYourTablewhere [id] notin (selectmax ([id]) fromYourTablegroup For example: id name value 1 a pp 2 a pp 3 B iii 4 B pp 5 B pp 6 c

Common SQL Problems: Select duplicates, eliminate duplicates, and select out sequences Example of a table: EMP Emp_no name Age 001 Tom 17 002 Sun 14 003 Tom 15 004 Tom 16 Requirements: List the records of all the people whose names are

Reference Address: http://blog.csdn.net/ccccalculator/article/details/70432123Because the use of group by in MySQL is always a 1055 error, which leads to the need to see what is the reason, query the relevant information, now note the notes, so that

Verification: MySQL Version 5.6Method One:Delete A from table a LEFT join (Select (ID) from table Group by Studentname,classid) b to a.id=b.id where b.id is null;Method Two:Explain delete from table where ID not in (select MiniD from (select min (id)

Pivot is used to rotate column values to column names (row to column), and SQL Server 2000 can be implemented with an aggregate function with a case statementThe general syntax for pivot is: Pivot (aggregate function (column) for column in (...)) As

Although the SQL statements for querying and deleting duplicate records are messy, the content is still good. Although the SQL statements for querying and deleting duplicate records are messy, the content is still good. For example: Id name value 1

You can understand group by and Aggregate functions in this way, groupbyTurn http://www.cnblogs.com/wuguanglei/p/4229938.html? Utm_source = tuicool; I personally think it is quite useful. In front of the article: It took a long time for group by to

Title: normal row/column conversion (Version 2.0) Note: normal row/column conversion (version 1.0) only provides static and dynamic writing for SQL Server 2000, and Version 2.0 adds SQL Server 2005 related writing.   Question: Suppose there is

For example: ID Name Value 1 a pp 2 a PP 3 B III 4 B pp 5 B pp 6 C pp 7 C pp 8 C III ID is primary key Ask for such a result ID Name Value 1 a pp 3 B III 4 B pp 6 C pp 8 C III Method 1 Delete yourtable where [id] not in ( Select MAX ([id]) from

Method 1:1, create a temporary table and select the data you want. 2, clear the original table. 3, temporary table data import into the original table. 4. Delete the temporary table. Mysql> SELECT * FROM student;+----+------+| ID | NAME |+----+------

SQL Server row and column conversion Pivot UnPivotPivot is used to rotate column values to column names (row to column), and SQL Server 2000 can be implemented with an aggregate function with a case statementThe general syntax for pivot is: Pivot

Pivot is used to rotate column values to column names (row to column), and SQL Server 2000 can be implemented with an aggregate function with a case statementThe general syntax for pivot is: Pivot (aggregate function (column) for column in (...)) As

Pivot is used to rotate column values to column names (row to column), and SQL Server 2000 can be implemented with an aggregate function with a case statementThe general syntax for pivot is: Pivot (aggregate function (column) for column in (...)) As

Pivot is used to rotate column values to column names (row to column), and SQL Server 2000 can be implemented with an aggregate function with a case statementThe general syntax for pivot is: Pivot (aggregate function (column) for column in (...)) As

SQL Row to Column rollupPivot is used to rotate column values to column names (row to column), and SQL Server 2000 can be implemented with an aggregate function with a case statementThe general syntax for pivot is: Pivot (aggregate function (column)