Group Functions with Non-group Selections in MySQL

Q

Can Group Functions Be Mixed with Non-group Selection Fields in MySQL?

✍: FYIcenter.com

A

If a group function is used in the SELECT clause, all other selection fields must be group level fields. Non-group fields can not be mixed with group fields in the SELECT clause. The script below gives you an example of invalid SELECT statements with group and non-group selection fields:

mysql> SELECT COUNT(*), url FROM fyi_links;
ERROR 1140 (42000): Mixing of GROUP columns 
   (MIN(),MAX(),COUNT(),...) with no GROUP columns
   is illegal if there is no GROUP BY clause

In this example, COUNT(*) is a group field and "url" is a non-group field.

⇒ Dividing Query Output into Groups in MySQL

⇐ Using Group Functions in the SELECT Clause in MySQL

⇑ SELECT Query Statements with GROUP BY in MySQL

⇑⇑ MySQL Database Tutorials

2017-10-16, 2361🔥, 0💬

Using Multiple Columns in GROUP BY in MySQL
Can Multiple Columns Be Used in GROUP BY in MySQL? If you want to break your output into smaller groups, if you specify multiple column names or expressions in the GROUP BY clause. Output in each group must satisfy a specific combination of the expressions listed in the GROUP BY clause. The more col... 2017-10-16, 2528🔥, 0💬

Using Group Functions in the SELECT Clause in MySQL
How To Use Group Functions in the SELECT Clause in MySQL? If group functions are used in the SELECT clause, they will be used on the rows that meet the query selection criteria, the output of group functions will be returned as output of the query. The following select statement returns 3 values cal... 2018-01-06, 2459🔥, 0💬

Count Number of Rows with SELECT Statements in MySQL
How To Use SELECT Statement to Count Number of Rows in MySQL? If you want to count the number of rows, you can use the COUNT(*) function in the SELECT clause. The following tutorial exercise shows you some good example: mysql> SELECT COUNT(*) FROM fyi_links; +----------+ | COUNT(*) | +-------... 2018-01-06, 2405🔥, 0💬

Group Functions with Non-group Selections in MySQL
Can Group Functions Be Mixed with Non-group Selection Fields in MySQL? If a group function is used in the SELECT clause, all other selection fields must be group level fields. Non-group fields can not be mixed with group fields in the SELECT clause. The script below gives you an example of invalid S... 2017-10-16, 2362🔥, 0💬

Counting Duplicated Values in a Column in MySQL
How To Count Duplicated Values in a Column in MySQL? If you have a column with duplicated values, and you want to know what are those duplicated values are and how many duplicates are there for each of those values, you can use the GROUP BY ... HAVING clause as shown in the following example. It ret... 2017-10-16, 2338🔥, 0💬

Using SELECT Statements in Views in MySQL
Can SELECT Statements Be Used on Views in MySQL? Select (query) statements can be used on views in the same way as tables. The following tutorial exercise helps you creating a view and running a query statement on the view: mysql> CREATE VIEW myLinks AS SELECT * FROM fyi_links WHERE url LIKE ... 2018-01-06, 2334🔥, 0💬

Apply Filtering Criteria at Group Level in MySQL
How To Apply Filtering Criteria at Group Level in MySQL? If you want to return only specific groups from the query, you can apply filtering criteria at the group level by using the HAVING clause inside the GROUP BY clause. Note group functions can also be used in HAVING conditions. The following tut... 2017-10-16, 2308🔥, 0💬

What Are Group Functions in MySQL
What Are Group Functions in MySQL? Group functions are functions applied to a group of rows. Examples of group functions are: COUNT(*) - Returns the number of rows in the group. MIN(exp) - Returns the minimum value of the expression evaluated on each row of the group. MAX(exp) - Returns the maximum ... 2018-01-06, 2264🔥, 0💬

Filerting out Duplications in Returning Rows in MySQL
How To Filter Out Duplications in Returning Rows in MySQL? If there are duplications in the returning rows, and you want to remove the duplications, you can use the keyword DISTINCT in the SELECT clause. The DISTINCT applies to the combination of all data fields specified in the SELECT clause. The t... 2018-01-06, 2231🔥, 0💬

All rights in the contents of this web site are reserved by the individual author. fyicenter.com does not guarantee the truthfulness, accuracy, or reliability of any contents.