POSTGRESQL SELECT DISTINCT HOW TO

PostgreSQL DISTINCT removes all duplicate rows and maintains only one row. Since social security numbers are unique already, you likely would have rare occasion to use a SELECT DISTINCT on the SocialSecurity column, as all records will likely already be unique by their very nature. The PostgreSQL DISTINCT clause keeps only one row for all groups of duplicate rows. If the COUNT DISTINCT function encounters NULL values, it ignores them unless every value in the specified column. However, let’s say there was only one instance of a name like “Dorjan”, then you would get the record for “Dorjan”. SELECT COUNT (DISTINCT itemnum) FROM items. For instance, if there are multiple instances of “Ronnie”, you would get no result.

You might want to return only information where the FirstName column contains only names that appear once in the table.

In the student table we are interested to know how many class records. For instance, if you have a table with data containing the following columns: DISTINCT command in SQL collects the unique or distinct records from a field of a table. The SELECT DISTINCT statement is used for cases where you only want to return values that are unique, distinct, or different from one another. 5 Answers Sorted by: 586 SELECT DISTINCT a,b,c FROM t is roughly equivalent to: SELECT a,b,c FROM t GROUP BY a,b,c It's a good idea to get used to the GROUP BY syntax, as it's more powerful.

POSTGRESQL SELECT DISTINCT HOW TO

You can read about regular SELECT SQL statements in our tutorial: How to Use the SQL SELECT Statement. In today’s database programming tutorial, we will learn how to use the SELECT DISTINCT statement to return only distinct – or unique – values from a table. In a previous tutorial, we discussed how to use the SQL SELECT statement to return values from a table.

Postgresql select distinct