REQUEST COMPLIMENTARY SQLS*PLUS LICENCE
PostgreSQL GROUP BY statement
PostgreSQL GROUP BY statement is used in the SELECT statement to collect data on several records and group results by one or more columns.
The syntax for GROUP BY statement in PostgreSQL
SELECT expression1_id, expression2_id,. expression_n_id,
aggregate_function
FROM tabs
[WHERE conds]
GROUP BY expression1_id, expression2_id,. expression_n_id;
Parameters and arguments of the statement
- expression1_id, expression2_id,…_n_id – Expressions that are not enclosed in an aggregate function and must be included in the GROUP BY offer.
- aggregate_function – This may be an aggregate function, for example, sum, count, min, max, or avg.
- Tabs – Tables from which you want to get records. At least one table must be specified in the FROM operator.
- WHERE conds – Optional. The conditions that must be met for the records to be selected.
Example using the sum function
Let’s consider an example of PostgreSQL query GROUP BY, which uses the sum function.
In this PostgreSQL example of GROUP BY, the sum function is used to return department names and “Salaries for the department”.
SELECT department, sum(salary_id) AS "Salaries for department".
FROM empls
GROUP BY depart;
Since you specified one column (department field) in your SELECT operator that is not encapsulated in the sum function, you should use the GROUP BY operator. That’s why the department field should be specified in the GROUP BY operator.
Example using the count function
Let’s consider how we could use the GROUP BY operator with the count function.
In this GROUP BY example, the count function is used to return department and “Number of employees” that have status ‘Active’.
SELECT department, count(*) AS "Number of employees"
FROM empls
WHERE status = 'Active'
GROUP BY depart;
Example using min function
Let’s now see how we can use the GROUP BY operator with the min function.
In this GROUP BY example, the function min is used to return department names and “Lowest salary”.
SELECT depart, min(salary_id) AS "Lowest salary".
FROM empls
GROUP BY depart;
Example using max
Finally, let’s see how we can use the GROUP BY operator with the max function.
In this GROUP BY example, the function max is used to get the department name and “Highest salary”.
SELECT department, max(salary_id) AS "Highest salary".
FROM empls
GROUP BY depart;
PostgreSQL: Group By | Course
MORE NEWS
PreambleNoSql is not a replacement for SQL databases but is a valid alternative for many situations where standard SQL is not the best approach for...
PreambleMongoDB Conditional operators specify a condition to which the value of the document field shall correspond.Comparison Query Operators $eq...
5 Database management trends impacting database administrationIn the realm of database management systems, moreover half (52%) of your competitors feel...
The data type is defined as the type of data that any column or variable can store in MS SQL Server. What is the data type? When you create any table or...
PreambleMS SQL Server is a client-server architecture. MS SQL Server process starts with the client application sending a query.SQL Server accepts,...
First the basics: what is the master/slave?One database server (“master”) responds and can do anything. A lot of other database servers store copies of all...
PreambleAtom Hopper (based on Apache Abdera) for those who may not know is an open-source project sponsored by Rackspace. Today we will figure out how to...
PreambleMongoDB recently introduced its new aggregation structure. This structure provides a simpler solution for calculating aggregated values rather...
FlexibilityOne of the most advertised features of MongoDB is its flexibility. Flexibility, however, is a double-edged sword. More flexibility means more...
PreambleSQLShell is a cross-platform command-line tool for SQL, similar to psql for PostgreSQL or MySQL command-line tool for MySQL.Why use it?If you...
PreambleWriting an application on top of the framework on top of the driver on top of the database is a bit like a game on the phone: you say “insert...
PreambleOracle Coherence is a distributed cache that is functionally comparable with Memcached. In addition to the basic function of the API cache, it...
PreambleIBM pureXML, a proprietary XML database built on a relational mechanism (designed for puns) that offers both relational ( SQL / XML ) and...
What is PostgreSQL array? In PostgreSQL we can define a column as an array of valid data types. The data type can be built-in, custom or enumerated....
PreambleIf you are a Linux sysadmin or developer, there comes a time when you need to manage an Oracle database that can work in your environment.In this...
PreambleStarting with Microsoft SQL Server 2008, by default, the group of local administrators is no longer added to SQL Server administrators during the...