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What Are Group Functions in Oracle
What Are Group Functions in Oracle? 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...
2019-12-19, 712👍, 0💬

Use of SELECT Statements in Views in Oracle
Can SELECT Statements Be Used on Views in Oracle? Select (query) statements can 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: SQL&gt; CREATE VIEW managed_dept AS SELECT * FROM departments WHERE manage...
2019-12-19, 652👍, 0💬

Filter Out Duplications in Returning Rows in Oracle
How To Filter Out Duplications in Returning Rows in Oracle? If there are duplications in the returning rows, and you want to remove the duplications, you can use the keyword DISTINCT or UNIQUE in the SELECT clause. The tutorial exercise below shows you that DISTINCT works on selected columns only: S...
2019-12-19, 639👍, 0💬

Sort Query Output in Descending Order in Oracle
How To Sort Query Output in Descending Order in Oracle? If you want to sort a column in descending order, you can specify the DESC keyword in the ORDER BY clause. The following SELECT statement first sorts the department in descending order, then sorts the salary in ascending order: SQL&gt; SELE...
2019-12-19, 633👍, 0💬

Concatenate Two Text Values in Oracle
How To Concatenate Two Text Values in Oracle? There are two ways to concatenate two text values together: CONCAT() function. '||' operation. Here is some examples on how to use them: SELECT 'FYI' || 'Center' || '.com' FROM DUAL; FYICenter.com SELECT CONCAT('FYICenter','.com') FROM DUAL; FYICenter.co...
2019-12-02, 1221👍, 0💬

Convert Times to Character Strings in Oracle
How To Convert Times to Character Strings in Oracle? You can convert dates to characters using the TO_CHAR() function as shown in the following examples: SELECT TO_CHAR(SYSDATE, 'HH:MI:SS') FROM DUAL; 04:49:49 SELECT TO_CHAR(SYSDATE, 'HH24:MI:SS.FF') FROM DUAL; -- Error: SYSDATE has no fractional se...
2019-12-02, 808👍, 0💬

What Is NULL Value in Oracle
What Is NULL Value in Oracle? NULL is a special value representing "no value" in all data types. NULL can be used on in operations like other values. But most operations has special rules when NULL is involved. The tutorial exercise below shows you some examples: SET NULL 'NULL'; -- Make sure NULL i...
2019-12-02, 795👍, 0💬

Convert Character Strings to Times in Oracle
How To Convert Character Strings to Times in Oracle? You can convert dates to characters using the TO_CHAR() function as shown in the following examples: SELECT TO_CHAR(TO_DATE('04:49:49', 'HH:MI:SS'), 'DD-MON-YYYY HH24:MI:SS') FROM DUAL; -- Default date is the first day of the current month 01-MAY-...
2019-12-02, 752👍, 0💬

Use NULL as Conditions in Oracle
How To Use NULL as Conditions in Oracle? If you want to compare values against NULL as conditions, you should use the "IS NULL" or "IS NOT NULL" operator. Do not use "=" or "&lt;&gt;" against NULL. The sample script below shows you some good examples: SELECT 'A' IS NULL FROM DUAL; -- Error: ...
2019-12-02, 752👍, 0💬

Divide Query Output into Groups in Oracle
How To Divide Query Output into Groups in Oracle? You can divide query output into multiple groups with the GROUP BY clause. It allows you specify a column as the grouping criteria, so that rows with the same value in the column will be considered as a single group. When the GROUP BY clause is speci...
2019-11-21, 791👍, 0💬

Group Functions Used with Non-group Selection Fields in Oracle
Can Group Functions Be Mixed with Non-group Selection Fields in Oracle? 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 ...
2019-11-21, 769👍, 0💬

Use Group Functions in the SELECT Clause in Oracle
How To Use Group Functions in the SELECT Clause in Oracle? 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 4 values ca...
2019-11-21, 724👍, 0💬

Count Duplicated Values in a Column in Oracle
How To Count Duplicated Values in a Column in Oracle? 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 re...
2019-11-21, 684👍, 0💬

Apply Filtering Criteria at Group Level in Oracle
How To Apply Filtering Criteria at Group Level in Oracle? 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. The following script gives you a good HAVING example: SQL&gt; SELECT dep...
2019-11-21, 638👍, 0💬

Use Multiple Columns in GROUP BY in Oracle
Can Multiple Columns Be Used in GROUP BY in Oracle? You can use multiple columns in the GROUP BY clause as shown in the following example. It returns how many employees are having the same salary in each department: SQL&gt; SELECT department_id, salary, count(*) 2 FROM employees GROUP BY departm...
2019-10-27, 824👍, 0💬

Query with an Inner Join in Oracle
How To Write a Query with an Inner Join in Oracle? If you want to query from two tables with an inner join, you can use the INNER JOIN ... ON clause in the FROM clause. The following query returns output with an inner join from two tables: employees and departments. The join condition is that the de...
2019-10-27, 823👍, 0💬

Use Group Functions in ORDER BY Clause in Oracle
Can Group Functions Be Used in the ORDER BY Clause in Oracle? If the query output is aggregated as groups, you can sort the groups by using group functions in the ORDER BY clause. The following statement returns how many employees are having the same salary in each department. The group output is so...
2019-10-27, 790👍, 0💬

Define and Use Table Alias Names in Oracle
How To Define and Use Table Alias Names in Oracle? When column names need to be prefixed with table names, you can define table alias name and use them to prefix column names as shown in the following select statement: SQL&gt; SELECT e.first_name, e.last_name, d.department_name FROM employees e ...
2019-10-27, 700👍, 0💬

Ways to Join Two Tables in a Single Query in Oracle
How To Join Two Tables in a Single Query in Oracle? Two tables can be joined together in a query in 4 ways: Inner Join: Returns only rows from both tables that satisfy the join condition. Left Outer Join: Returns rows from both tables that satisfy the join condition, and the rest of rows from the fi...
2019-10-27, 615👍, 0💬

Query with a Left Outer Join in Oracle
How To Write a Query with a Left Outer Join in Oracle? If you want to query from two tables with a left outer join, you can use the LEFT OUTER JOIN ... ON clause in the FROM clause. The following query returns output with a left outer join from two tables: departments and employees. The join conditi...
2019-10-18, 777👍, 0💬

Query with a Full Outer Join in Oracle
How To Write a Query with a Full Outer Join in Oracle? If you want to query from two tables with a full outer join, you can use the FULL OUTER JOIN ... ON clause in the FROM clause. The following query returns output with a full outer join from two tables: departments and employees. The join conditi...
2019-10-18, 769👍, 0💬

Left Outer Join with the WHERE Clause in Oracle
How To Write a Left Outer Join with the WHERE Clause in Oracle? If you don't want to use the LEFT OUTER JOIN ... ON clause to write a left outer join, you can use a special criteria in the WHERE clause as "left_table.column = right_table.column(+)". The select statement below is an example of a left...
2019-10-18, 760👍, 0💬

Inner Join with the WHERE Clause in Oracle
How To Write an Inner Join with the WHERE Clause in Oracle? If you don't want to use the INNER JOIN ... ON clause to write an inner join, you can put the join condition in the WHERE clause as shown in the following query example: SQL&gt; SELECT d.department_name, e.first_name, e.last_name 2 FROM...
2019-10-18, 748👍, 0💬

Query with a Right Outer Join in Oracle
How To Write a Query with a Right Outer Join in Oracle? If you want to query from two tables with a right outer join, you can use the RIGHT OUTER JOIN ... ON clause in the FROM clause. The following query returns output with a right outer join from two tables: departments and employees. The join con...
2019-10-18, 707👍, 0💬

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