The table has an index on (clicked at time zone 'PST'). If it is required to eliminate the duplicate rows from the resultant table the DISTINCT clause in PostgreSQL can be used. Mnemonic: DISTINCT means different which is what '<>' tests for . I am trying to get a distinct set of rows from 2 tables. PostgreSQL DISTINCT. (Remember, these queries return the exact same results.) Jump to: navigation, search. The PostgreSQL distinct keyword is used to return unrepeated results of an attribute so only one instance of repeated values is displayed. The PostgreSQL DISTINCT clause is used with a SELECT statement to suppress duplicate values if any in a column. We can also compare the execution plans when we change the costs from CPU + I/O combined to I/O only, a feature exclusive to Plan Explorer . Is there any dissadvantage of using "group by" to obtain a unique list? SELECT -- 3 rows a.house, -- 12 rows (for each house) a.id, -- for each ID (there are 4 repeating records) -- out of these 4 records, only 1 is unique while remaining are -- repeated records a.points FROM records a group by a.house order by a.house, a.id I have two tables, player and card (a card represents something like a hitman's contract, with a reference to the 'killer' and the 'victim' which both reference the player table). After comparing on multiple machines with several tables, it seems using group by to obtain a distinct list is substantially faster than using select distinct. After looking at someone else's query I noticed they were doing a group by to obtain the unique list. PostgreSQL wiki explain IS DISTINCT FROM: IS DISTINCT FROM and IS NOT DISTINCT FROM … treat NULL as if it was a known value, rather than … EF Core currently pushes down a select expression into a subquery, since a projection would make the results different (SQL DISTINCT operates over the selected columns, whereas C# Distinct() operates on the entire entity). The DISTINCT variation took 4X as long, used 4X the CPU, and almost 6X the reads when compared to the GROUP BY variation. Hard to believe. GROUP BY vs DISTINCT; Brian Herlihy. After executing a select statement the resultant table returns all rows according to the provided expression. SELECT DISTINCT on two columns not exactly what I want Hi r/PostgreSQL ! From PostgreSQL wiki. Pg supports two comparison statements IS DISTINCT FROM and IS NOT DISTINCT FROM, these essentially treat NULL as if it was a known value, rather than a special case for unknown. Dec 20, 2006 at 7:26 am: I have a question about the following. In this section, we are going to understand the working of the PostgreSQL DISTINCT clause, which is used to delete the matching rows or data from a table and get only the unique records.. The distinct keyword is very useful and is often used with a SELECT statement in PostgreSQL. Note: The DISTINCT clause is only used with the SELECT command. I am using postgres 8.1.3 Actually, I think I answered my own question already. The main difference between Unique and Distinct in SQL is that Unique helps to ensure that all the values in a column are different while Distinct helps to remove all the duplicate records when retrieving the records from a table.. Generally, SQL or Structure Query Language is the language that allows performing various operations on the data stored in the databases of the RDBMS. "Haywood J'Bleauxmie" writes: > The first SELECT does NOT work in that the distinct() is ignored. 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