How To Define and Use Table Alias Names

Q

How To Define and Use Table Alias Names? - Oracle DBA FAQ - Understanding SQL SELECT Query Statements

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A

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> SELECT e.first_name, e.last_name, d.department_name
  FROM employees e INNER JOIN departments d 
  ON e.department_id=d.department_id;
FIRST_NAME           LAST_NAME            DEPARTMENT_NAME
-------------------- -------------------- ---------------
Steven               King                 Executive
Neena                Kochhar              Executive
Lex                  De Haan              Executive
Alexander            Hunold               IT
Bruce                Ernst                IT
David                Austin               IT
Valli                Pataballa            IT
......

2007-04-19, 5843👍, 0💬

How To Define and Use Table Alias Names
How To Define and Use Table Alias Names? - Oracle DBA FAQ - Understanding SQL SELECT Query Statements 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> SELECT e.first_name, e.la... 2007-04-19, 5844👍, 0💬

How To Write a Query with a Left Outer Join
How To Write a Query with a Left Outer Join? - Oracle DBA FAQ - Understanding SQL SELECT Query Statements 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 ... 2007-04-19, 5565👍, 0💬

How To Write a Left Outer Join with the WHERE Clause
How To Write a Left Outer Join with the WHERE Clause? - Oracle DBA FAQ - Understanding SQL SELECT Query Statements 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(+)".... 2007-04-19, 5552👍, 0💬

How To Join Two Tables in a Single Query
How To Join Two Tables in a Single Query? - Oracle DBA FAQ - Understanding SQL SELECT Query Statements 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 t... 2007-04-20, 5448👍, 0💬

How To Write an Inner Join with the WHERE Clause
How To Write an Inner Join with the WHERE Clause? - Oracle DBA FAQ - Understanding SQL SELECT Query Statements 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> SELECT d.depar... 2007-04-19, 5381👍, 0💬

How To Write a Query with a Full Outer Join
How To Write a Query with a Full Outer Join? - Oracle DBA FAQ - Understanding SQL SELECT Query Statements 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 ... 2007-04-19, 5333👍, 0💬

Can Multiple Columns Be Used in GROUP BY
Can Multiple Columns Be Used in GROUP BY? - Oracle DBA FAQ - Understanding SQL SELECT Query Statements 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> SELECT department_id, salary... 2007-04-20, 5306👍, 0💬

How To Write a Query with an Inner Join
How To Write a Query with an Inner Join? - Oracle DBA FAQ - Understanding SQL SELECT Query Statements 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... 2007-04-19, 5259👍, 0💬

How To Count Duplicated Values in a Column
How To Count Duplicated Values in a Column? - Oracle DBA FAQ - Understanding SQL SELECT Query Statements 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 ... HAV... 2007-04-20, 5105👍, 0💬

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