Column ambiguously defined oracle ошибка

SELECT  DISTINCT  
        per_all_people_f.EMPLOYEE_NUMBER 
        , MAX(per_all_people_f.LAST_UPDATE_DATE) 
        , per_all_people_f.KNOWN_AS  FULL_NAME
        , to_char(notified_termination_date, 'DD-MM-YYYY') AS termination_date 
        , :FROM_DATE  DATE1
        , :TO_DATE DATE2
--      , D_LEAVING_REASON AS D_LEAVING_REASON
        , CASE substr(substr(hr_all_organization_units_tl.NAME, instr(hr_all_organization_units_tl.NAME, '.') + 1), 1, 1)
        WHEN 'B'  THEN
            'إدارة الاتصالات وتقنية المعلومات'
        WHEN 'C'  THEN
            'إدارة المشاريع'
        WHEN 'D'  THEN
            'الإدارة القانونية'
        WHEN 'E'  THEN
            'إدارة الصحه والسلامة والبيئه'
        WHEN 'F'  THEN
            'إدارة هندسة المكامن والانتاج'
        WHEN 'G'  THEN
            'إدارة الهندسة'
        WHEN 'H'  THEN
            'إدارة العمليات'
        WHEN 'J'  THEN
            'إدارة الحفر وصيانة الآبار'
        WHEN 'K'  THEN
            'إدارة المواد'
        WHEN 'L'  THEN
            'إدارة النقل والخدمات'
        WHEN 'M'  THEN
            'إدارة الاستكشاف'
        WHEN 'N'  THEN
            'إدارة فرع بنغازي'
        WHEN 'P'  THEN
            'إدارة التخطيط'
        WHEN 'R'  THEN
            'إدارة المالية'
        WHEN 'T'  THEN
            'إدارة المراجعه'
        WHEN 'W'  THEN
            'إدارة التدريب والتطوير'
        WHEN 'Y'  THEN
            'إدارة شؤون الموظفين'
            else case  substr(substr(hr_all_organization_units_tl.NAME, instr(hr_all_organization_units_tl.NAME, '.') + 1), 1, 3)
              WHEN 'A11'  THEN
            'لجنة المناقصات'
        WHEN 'A10'  THEN
            'لجنة الادارة'
        WHEN 'A12'  THEN
            'قسم الاعلام '
            end
        END  DEPARTMENT
    , CASE d_leaving_reason 
        WHEN 'Retirement'  THEN
            'التقاعد'
        END 
        LEAVING_REASON1 
FROM    per_all_people_f
LEFT JOIN per_periods_of_service_v ON per_all_people_f.person_id = per_periods_of_service_v.person_id
LEFT JOIN per_assignments_f ON per_all_people_f.EMPLOYEE_NUMBER = per_assignments_f.ASSIGNMENT_NUMBER
LEFT JOIN hr_all_organization_units_tl ON per_assignments_f.ORGANIZATION_ID = hr_all_organization_units_tl.ORGANIZATION_ID
WHERE   notified_termination_date >= TO_DATE(:FROM_DATE,'MM-YYYY') AND notified_termination_date <= TO_DATE(:TO_DATE,'MM-YYYY')
--      AND D_LEAVING_REASON = 'Retirement'
        AND CURRENT_EMPLOYEE_FLAG IS NULL AND employee_number IS NOT NULL
GROUP BY EMPLOYEE_NUMBER,d_leaving_reason,LAST_UPDATE_DATE,KNOWN_AS,notified_termination_date
,:FROM_DATE,:TO_DATE,NAME

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ORA-00918: колонка неясно (неоднозначно) определена

Причина:

имя колонки используемой в объединении используется в более чем одной таблице, и поэтому ссылка понимается неоднозначно. В объединении, любая колонка которая присутствует в более чем одной таблице должна быть префиксирована своим именем таблицы на которую ссылаются. На колонку ссылаются TABLE.COLUMN или TABLE _ALIAS.COLUMN. Например, если соединяются таблицы EMP и DEPT и они обе содержат колонку DEPTNO, то все ссылки на DEPTNO должны быть префиксированы именем таблицы, как EMP.DEPTNO или E.DEPTNO.

Действие:

Префиксируйте ссылки на имена колонок, которые существуют в объединенных таблицах именем таблицы или сокращением имени таблицы, при этом ставьте точку как показано в примере выше.

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Ora 00918 column ambiguously defined means that your Oracle database is unable to determine which table a column belongs to because you specified it in more than one table in your query.

This is a rather complex error message to troubleshoot, but this article will teach you why you’re seeing the error and methods that can fix the ambiguity in your query.

After reading this article, you’ll know more about the Oracle database, and you can solve this error if you see it again. That being said, get your query ready and launch your Oracle database because we’re about to teach you how to resolve ORA-00918 column ambiguously defined.

Contents

Why Do You Have Ambiguity in Your Column Names?
- – You’re Using a Column Name Multiple Times in Your Query
How To Fix the Ambiguity in Your Column Names?
- – Used the Table Name To Identify the Column
- – Use Table Aliases To Refer to the Column Name
- – Use a Subquery for Unique Column Names
- – Avoid the Asterisks Sign In Your “Select” Statements
- – Rename the Columns
Conclusion

Why Do You Have Ambiguity in Your Column Names?

You have ambiguity in your column names because you’re using a column name multiple times in your SQL query. As a result, the Oracle database cannot know which table the column belongs to, so it throws the ORA-00918 error in response.

– You’re Using a Column Name Multiple Times in Your Query

The ambiguity error in your SQL query occurred because you’re using a column name multiple times. As a result, the database does not know which table the column belongs to, and it throws the “ORA-00918 column ambiguously defined Oracle” error message.

For example, in the following, we have two tables, PC_Mechanic and PC_Fixing_Cost, and both tables have the “mechanic_id” column. Then the “SELECT” statement is trying to find the mechanic that fixed a particular PC, but the query is ambiguous.

That’s because the “mechanic_id” column exists in the PC_Mechanic and the PC_Fixing_Cost table. So, the Oracle database does not know which table the “mechanic_id” belongs to, and it throws the ambiguity error.

CREATE TABLE PC_Mechanic (

mechanic_id int primary key,

mechanic_name varchar2(50) not null

);

CREATE TABLE PC_Fixing_Cost (

cost_id int primary key,

mechanic_id int not null,

cost_amount int not null

);

SELECT mechanic_id

FROM PC_Mechanic, PC_Fixing_Cost

WHERE PC_Mechanic.mechanic_id = PC_Fixing_Cost.mechanic_id;

How To Fix the Ambiguity in Your Column Names?

To correct ambiguous column names in your SQL query, do any of the following:

Used the table name to identify the column
Use table aliases to refer to the column name
Use a sub-query for unique column names
Avoid the asterisks sign in your SELECT statements
Rename the columns

– Used the Table Name To Identify the Column

When an ambiguity error occurs, you can use a table name to identify the column. By doing this, the Oracle database knows where the column belongs and will not raise the ORA-00918 error.

For example, in our PC mechanic example, you can update the “SELECT” statement by adding the table name (“PC_Mechanic”) as the prefix to the first “mechanic_id” in the query. This will prevent the ORA-00918 error, and the code will work as expected.

— Add the table name to differentiate the column

SELECT PC_Mechanic.mechanic_id

FROM PC_Mechanic, PC_Fixing_Cost

WHERE PC_Mechanic.mechanic_id = PC_Fixing_Cost.mechanic_id;

Now, if your SQL is different from the one above, you can use the same approach to resolve the ambiguity error. For example, in the following, we have a “college” and a “staff” table with different table structures.

The error in the code is the “SELECT” statement that’s using the “college_id” in the “WHERE” condition. This should work, but both tables have the “college_id” column that will confuse the database when you run the code.

CREATE TABLE college (

college_id number PRIMARY KEY,

college_name varchar2(50)

);

CREATE TABLE staff (

staff_id number PRIMARY KEY,

name varchar2(50),

college_id number, foreign key(college_id) references college(college_id)

);

SELECT * FROM college, staff WHERE college_id = 1;

The solution to the error in the previous SELECT statement is to prefix the college_id in the WHERE clause with the table name.

–Fix: Use the table name of the college_id column

SELECT * FROM college, staff WHERE college.college_id = 1;

– Use Table Aliases To Refer to the Column Name

You can use aliases to solve the “ORA-00918 column ambiguously defined subquery” error, and here, we’ll show you how it works. First, in your Oracle database, you can assign unique names to your column names to prevent an ambiguity error.

For example, in the “SELECT” statement in the following SQL, we want an SQL self-join, but an ambiguity error occurs because we repeated the table name twice.

CREATE TABLE human_resource (

hr_id number PRIMARY KEY,

hr_name varchar2(50)

);

CREATE TABLE staff_tb (

id number PRIMARY KEY,

staff_name varchar2(50),

manager_id number, foreign key(manager_id) references human_resource(hr_id)

);

— This will cause an error

SELECT * FROM staff_tb, staff_tb WHERE id = manager_id;

The fix is to give both table aliases and use them in the SELECT query and with this, the previous SELECT query becomes the following:

SELECT * FROM human_resource mgr, staff_tb emp where mgr.hr_id=emp.id;

Finally, the following variation of the SELECT query also works, and you can use the same to solve the “column ambiguously defined join” error.

SELECT s.*, m.*

FROM staff_tb s

JOIN staff_tb m ON s.manager_id = m.id;

– Use a Subquery for Unique Column Names

In Oracle SQL, subqueries can solve the “column ambiguously defined SQL” error in your Oracle database. Generally, a subquery provides a means to retrieve data that will be used in the main query as a filter condition.

Here, you’ll use them to assign a unique column name to your column so that the Oracle database can differentiate it from other columns with the same name. To show how this works, the “SELECT” query in the following code will cause the ORA-00918 error because the “school_id” column is present in the “school” and “principals” tables.

CREATE TABLE school(

school_id number PRIMARY KEY,

school_name varchar2(50)

);

CREATE TABLE principals(

id number PRIMARY KEY,

name varchar2(50),

school_id number, foreign key(school_id) references school(school_id)

);

— The following will not work.

SELECT * FROM school, principals WHERE school_id=1;

We can fix this error by using a sub-query that assigns a new name to the “school_id” column of the “principals” table:

SELECT * FROM school, (SELECT school_id schoolid FROM principals) WHERE school_id=1;

– Avoid the Asterisks Sign In Your “Select” Statements

If you can avoid asterisks in your SQL code, please do, but in certain cases, you’ll need them as shown in our previous “column ambiguously defined examples. What’s more, the following are reasons why you might want to avoid asterisks in your SQL query, especially in a production environment:

Performance: When you use an asterisk in a SQL query, you are asking the database to retrieve all columns in the table. This can be very inefficient, especially if the table has many columns.
Future changes: If the table schema changes and new columns are added, using an asterisk can result in unexpected results. For example, your queries can start retrieving columns that you don’t want.
Security: Using asterisks can potentially give users more access to data than they should have if your application has any security concerns.

– Rename the Columns

Renaming your table columns should be your last resort if all else fails. In Oracle database, you can rename a column using the “ALTER TABLE” statement with the “RENAME COLUMN” clause.

ALTER TABLE table_name RENAME COLUMN old_column_name TO new_column_name;

For example, the following SQL will rename the column “salary” in the table “employees” to “monthly_salary.

ALTER TABLE employees RENAME COLUMN salary TO monthly_salary;

Finally, note that renaming a column can cause data type or length changes. So, this can require additional changes to dependent objects, such as indexes and views.

As a result, we advise that you test the impact of renaming a column before implementing it in a production environment.

Conclusion

This article explained why Oracle databases throw the ORA-00918 error and how you can modify your SQL queries to prevent the error. We’ll leave you with the following summary:

Multiple columns in your SQL queries is the reason why you see “ORA-00918 column ambiguously defined” is Oracle database.
To solve “ORA-00918 column ambiguously defined”, use the table name to differentiate the column or use table aliases.
You can also use sub-queries to assign unique names to your columns if there is a possibility of ORA-00918 error.
If possible, avoid asterisks in your “SELECT” statements and be specific about what you need from your Oracle database.
The last resort to solve ORA-00918, is to rename your column using “ALTER TABLE” with the “RENAME COLUMN” clause.

That ends our discussion of ORA-00918 in Oracle databases and how you can resolve it. Every Oracle database developer that’s seeing this error will appreciate it if you show them this article, so kindly do that.

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В этом посту вы узнаете, что значит ошибка «ORA-00918: column ambiguously defined» и как её решить. Ошибка возникает, когда при объединении в двух таблицах присутствуют колонки с одинаковым названием и непонятно, к какой таблице относится колонка.

Для воспроизведения ошибки, создаём две простых таблицы с одинаковыми колонками — цифровой и текстовой. И number_column, и text_column присутствуют в обоих таблицах.

CREATE TABLE test_table1(number_column NUMBER, text_column VARCHAR2(50) )

CREATE TABLE test_table2(number_column NUMBER, text_column VARCHAR2(50) )

Выпоняем запрос SQL с объединением через JOIN, выбираем значения number_column, text_column из таблиц test_table1 и test_table2, в которых number_column из одной равняется number_column из другой, и number_column равняется единице.

SELECT number_column, text_column FROM test_table1 JOIN test_table2 ON number_column = number_column WHERE number_column = 1

Уже прочитав предложение сразу становится понятным, что невозможно определить к какой из двух таблиц относится number_column, а также text_column, что менее очевидно. После выполнения запроса Apex SQL Workshop (или любой другой инструмент для работы с базами данных Oracle) выдаёт такую ошибку:

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CREATE TABLE test_table1(number_column NUMBER, text_column VARCHAR2(50) )

CREATE TABLE test_table2(number_column NUMBER, text_column VARCHAR2(50) )

SELECT number_column, text_column FROM test_table1 JOIN test_table2 ON number_column = number_column WHERE number_column = 1

Скриншот 1: Ошибка ORA-00918: column ambiguously defined

Исправить ситуацию можно двумя методами. В первом просто прописывает название таблицы перед названием колонки.

SELECT test_table1.number_column, test_table1.text_column FROM test_table1 JOIN test_table2 ON test_table1.number_column = test_table2.number_column WHERE test_table1.number_column = 1

Второй метод удобнее. В нём используются алиасы названий таблиц, в нашем примере t1 для test_table1 и t2 для test_table2.

SELECT t1.number_column, t1.text_column FROM test_table1 t1 JOIN test_table2 t2 ON t1.number_column = t2.number_column WHERE t1.number_column = 1

Кстати, в MySQL эта ошибка называется «#1052 — Column ‘number_column’ in field list is ambiguous» и лечится тем же способом. phpMyAdmin выдаёт при такой ошибке следующее сообщение:

Скриншот 2: Ошибка MySQL #1052 — Column in field list is ambiguous

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Learn the cause and how to resolve the ORA-00918 error message in Oracle.

Description

When you encounter an ORA-00918 error, the following error message will appear:

ORA-00918: column ambiguously defined

Cause

You tried to execute a SQL statement that joined two or more tables, where a column with the same name exists in both tables.

Resolution

The option(s) to resolve this Oracle error are:

Option #1

Prefix the column with the table name and then re-execute the statement.

For example, if you tried to execute the following SQL statement:

SELECT supplier_id, quantity
FROM suppliers
INNER JOIN orders
ON suppliers.supplier_id = orders.supplier_id;

You would receive the following error message:

Since the supplier_id column exists in both the suppliers and orders table, you need to prefix the column with the table name as follows:

SELECT suppliers.supplier_id, quantity
FROM suppliers
INNER JOIN orders
ON suppliers.supplier_id = orders.supplier_id;

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