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Does SELECT distinct apply to all columns?
The DISTINCT keyword is applied to all columns. It means that the query will use the combination of values in all columns to evaluate the distinction. If you want to select distinct values of some columns in the select list, you should use the GROUP BY clause.
Can we use distinct for more than one column?
Answer. Yes, the DISTINCT clause can be applied to any valid SELECT query. It is important to note that DISTINCT will filter out all rows that are not unique in terms of all selected columns.
What is the purpose of SELECT distinct?
The SELECT DISTINCT statement is used to return only distinct (different) values. Inside a table, a column often contains many duplicate values; and sometimes you only want to list the different (distinct) values.
Can you select distinct on multiple columns in SQL?
The problem with your query is that when using a GROUP BY clause (which you essentially do by using distinct) you can only use columns that you group by or aggregate functions. You cannot use the column id because there are potentially different values.
Can a distinct value be passed into a unique index?
Also passes in a unique index and almost anywhere else, since NULL values do not compare equal according to the SQL standard. See: OTOH, GROUP BY, DISTINCT or DISTINCT ON () treat NULL values as equal.
Can a column ID be used in a column?
You cannot use the column id because there are potentially different values. In your case there is always only one value because of the HAVING clause, but most RDBMS are not smart enough to recognize that.
Can a null value be treated as distinct in SQL?
This query (unlike the currently accepted answer by Joel) does not treat NULL values as equal. The following two rows for (saleprice, saledate) would qualify as “distinct” (though looking identical to the human eye): Also passes in a unique index and almost anywhere else, since NULL values do not compare equal according to the SQL standard. See: