Postgresql replace null with 0 left join8/24/2023 There has got to be a way to run the original three-condition query in a way that does not match on nulls or empty values, but I have not yet found it. This looks like it should work, but it dies at the first WHERE clause.Īm I on the right track here? How can I make this work? Or is there another approach that works much better? OR (People.CellNumber = Stuff.PhoneNumber In this iteration, I have come up with the following: SELECT * The problem in the current approach is that whenever I must make changes to the query, I must make them in multiple places in the code, which makes for a maintenance nightmare. But now I need to revamp this script to accommodate changes in business need, and I am trying to find once again a simpler solution. I have been using this very non-elegant approach for years, and it has worked with no problems. SELECT *ĭump the matched records into a temp table, then run the non-matched records through the second query: SELECT *ĭump the matched records into the temp table, then run the remaining non-matched records through the third query: SELECT *ĭump the result (both matched and non-matched) into the temp table, and move on. I searched for weeks and never did find an elegant or simple way around this, so I finally had to break it up into a series of separate queries as follows. It does the same with nulls, and for all three comparisons. Third, specify the right table (table B) in the LEFT JOIN clause and the join condition after the ON. Second, specify the left table (table A) in the FROM clause. The result is that it takes every record with an empty cell in the People table and joins it with every record in the Stuff table with an empty cell. To join the table A with the table B table using a left join, you follow these steps: First, specify the columns in both tables from which you want to select data in the SELECT clause. When I first tried to run this query, it produced millions of records in the joined table, not at all what I expected.Īfter days of troubleshooting, I finally determined that it was the presence of nulls and empty cells that was causing this enormous increase in the results.įor those who might not know, PostgreSQL treats nulls and empty cells with the same respect as cells with data in them. The original query I wrote years ago to do this was as follows: SELECT * These columns may or may not have values in them, or they may even contain nulls. There are three columns which I can use to find possible matches: person ID, phone number or email address. I have a large table (250,000+ rows, 100+ columns) named People, and another called Stuff, which may or may not contain a corresponding record. I call this my " Battle of the Nulls", for I have struggled with this issue for years now.
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