![]() ![]() You can either use the above syntax or the below syntax.SELECT expression1, expression2. This example sorts the results based on the salary column and displays the first three rows only from the query: postgres=# select ename,sal from emp order by sal OR postgres=# select ename,sal from emp order by sal ' This example sorts the results based on the salary column and displays only the first row/record from the query: postgres=# select ename,sal from emp order by sal postgres=# select ename,sal from emp order by sal NOTE: You should use the FETCH clause with the ORDER BY clause to get a consistent result, as the order of rows stored in a table is unpredictable. The FETCH clause is used to limit the number of retrieved portions of rows generated by a query. The ‘_’ below denotes one character only: postgres=# select ename from emp where ename like '_L%' This example lists the employee names whose second letter is the letter L. ![]() The ‘%’ below denotes zero or many characters: postgres=# select ename from emp where ename like 'S%' This example lists the employees with names starting with letter S. The LIKE condition is used to match a character pattern in wild-card searches. Postgres=# select ename,sal from emp where ename between 'ALLEN' and 'JONES' This example sorts and displays the results between two character values: postgres=# select empno,ename from emp order by ename Here BETWEEN is used to look for salaries with a value greater than or equal to 500 and less than or equal to 1000: postgres=# select ename,sal from emp where sal between 5 The BETWEEN operator can be used to find out the range between two values. Postgres=# select deptno, AVG(sal) from emp group by deptno having AVG(sal) > 300 LINE 1: select deptno, AVG(sal) from emp where AVG(sal) > 300 group. ExampleĪttempting to use WHERE and GROUP BY together will give an error: postgres=# select deptno, AVG(sal) from emp where AVG(sal) > 300 group by deptno ĮRROR: aggregate functions are not allowed in WHERE ![]() The WHERE clause cannot be used to restrict groups. Results of a GROUP BY clause can be restricted to those satisfying certain conditions using the HAVING clause. NOTE: All columns in the list that are not in grouped functions must be included in the GROUP BY clause. This example displays departments with the average salary for their employees: select deptno, avg(sal) from emp group by deptno The rows in a table can be condensed into a smaller number groups that share the same value by using the GROUP BY clause. Example postgres=# select empno,ename,deptno from emp where ename='KING' postgres=# select empno, ename, deptno from emp where deptno=10 Ĭharacter strings and dates can also be used in a WHERE clause. This example lists only the data of the employees who are working in the department number 10. The WHERE clause is used to restrict the data to rows that match specific conditions. To restrict the data to be retrieved from a table to specific columns, specify them after the SELECT keyword: postgres=# select empno,ename from emp Using the asterisk symbol (*) with SELECT will list all the columns in their defined order: postgres=# select * from emp Įmpno | ename | job | mgr | hiredate | sal | comm | deptno This example shows that all the columns can be retrieved using the FROM clause. The FROM clause is used to specify the table or tables that data is retrieved from. Let’s take a look at some of the most common clauses and how you can make best use of them when querying data in PostgreSQL. It introduces different clauses and provides examples of their usage.Ĭlauses are helpful and often necessary components of a search query to help filter and organize data. SUMMARY: This article discusses the use of clauses in PostgreSQL queries to filter and organize data in results.
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