Taming the Two-Faced Column: How to Fix Duplicate Column Errors in PostgreSQL Views

Using SELECT *:

CREATE VIEW my_view AS
SELECT * 
FROM table1, table2;

-- Error: column "id" specified more than once

Both table1 and table2 might have an "id" column, leading to the error.

Explicitly selecting duplicates:

CREATE VIEW my_view AS
SELECT column1, column1 AS duplicate_name
FROM my_table;

-- Error: column "column1" specified more than once

You've selected column1 twice with different aliases, which is still considered a duplicate.

Joining tables with duplicate names:

CREATE VIEW my_view AS
SELECT table1.name, table2.name
FROM table1 JOIN table2 ON table1.id = table2.id;

-- Error: column "name" specified more than once

Both tables have a "name" column. Without aliases, the view doesn't know which one to use.

1. List specific columns instead of SELECT *:

CREATE VIEW my_view AS
SELECT table1.id, table2.column_x, table1.column_y
FROM table1, table2;

This ensures each column has a unique name in the view.

1. Use aliases for duplicate column names:

CREATE VIEW my_view AS
SELECT column1, column1 AS alias_name
FROM my_table;

By assigning an alias, you differentiate between the two occurrences of column1.

1. Use aliases when joining tables with duplicate names:

CREATE VIEW my_view AS
SELECT table1.name AS table1_name, table2.name AS table2_name
FROM table1 JOIN table2 ON table1.id = table2.id;

Adding aliases clarifies which "name" column belongs to which table.

• Missing column names: If you specify fewer column names in the CREATE VIEW statement than the SELECT clause actually returns, you'll get an error. Make sure the number of columns matches.
• Incorrect table names: Ensure you're referencing tables correctly in your view definition. Typos can cause unexpected behavior.