The distinct keyword is very useful and is often used with a SELECT statement in PostgreSQL. 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. Jump to: navigation, search. 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 After looking at someone else's query I noticed they were doing a group by to obtain the unique list. Hard to believe. Dec 20, 2006 at 7:26 am: I have a question about the following. I am trying to get a distinct set of rows from 2 tables. The PostgreSQL distinct keyword is used to return unrepeated results of an attribute so only one instance of repeated values is displayed. Is there any dissadvantage of using "group by" to obtain a unique list? 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). If it is required to eliminate the duplicate rows from the resultant table the DISTINCT clause in PostgreSQL can be used. SELECT DISTINCT on two columns not exactly what I want Hi r/PostgreSQL ! I am using postgres 8.1.3 Actually, I think I answered my own question already. 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). PostgreSQL DISTINCT. "Haywood J'Bleauxmie" writes: > The first SELECT does NOT work in that the distinct() is ignored. From PostgreSQL wiki. 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.. After executing a select statement the resultant table returns all rows according to the provided expression. 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. Note: The DISTINCT clause is only used with the SELECT command. 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. The table has an index on (clicked at time zone 'PST'). 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 . The PostgreSQL DISTINCT clause is used with a SELECT statement to suppress duplicate values if any in a column. 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 … Mnemonic: DISTINCT means different which is what '<>' tests for . I have a query which selects number of records for each house. GROUP BY vs DISTINCT; Brian Herlihy. The DISTINCT variation took 4X as long, used 4X the CPU, and almost 6X the reads when compared to the GROUP BY variation. (Remember, these queries return the exact same results.) If it is required to eliminate the duplicate rows from the resultant returns! Question about the following columns not exactly what I want Hi r/PostgreSQL tests for which is what <. Is often used with the SELECT command these queries return the exact results! 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