29 Sep 2014

PostgreSQL: ERROR: column does not exist

I’ve been playing around with PostgreSQL recently and in particular the Northwind dataset typically used as an introductory data set for relational databases.

Having imported the data I wanted to take a quick look at the employees table:

postgres=# select * from employees limit 1;
 EmployeeID | LastName | FirstName |        Title         | TitleOfCourtesy | BirthDate  |  HireDate  |           Address           |  City   | Region | PostalCode | Country |   HomePhone    | Extension | Photo |                                                                                      Notes                                                                                      | ReportsTo |              PhotoPath
------------+----------+-----------+----------------------+-----------------+------------+------------+-----------------------------+---------+--------+------------+---------+----------------+-----------+-------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------+--------------------------------------
          1 | Davolio  | Nancy     | Sales Representative | Ms.             | 1948-12-08 | 1992-05-01 | 507 - 20th Ave. E.\nApt. 2A | Seattle | WA     | 98122      | USA     | (206) 555-9857 | 5467      | \x    | Education includes a BA in psychology from Colorado State University in 1970.  She also completed "The Art of the Cold Call."  Nancy is a member of Toastmasters International. |         2 | http://accweb/emmployees/davolio.bmp
(1 row)

That works fine but what if I only want to return the 'EmployeeID' field?

postgres=# select EmployeeID from employees limit 1;
ERROR:  column "employeeid" does not exist
LINE 1: select EmployeeID from employees limit 1;

I hadn’t realised (or had forgotten) that field names get lower cased so we need to quote the name if it’s been stored in mixed case:

postgres=# select "EmployeeID" from employees limit 1;
 EmployeeID
------------
          1
(1 row)

From my reading the suggestion seems to be to have your field names lower cased to avoid this problem but since it’s just a dummy data set I guess I’ll just put up with the quoting overhead for now.

About the author

I'm currently working on short form content at ClickHouse. I publish short 5 minute videos showing how to solve data problems on YouTube @LearnDataWithMark. I previously worked on graph analytics at Neo4j, where I also co-authored the O'Reilly Graph Algorithms Book with Amy Hodler.