Is there a difference between unique and distinct?
Unique was the old syntax while Distinct is the new syntax,which is now the Standard sql. Unique creates a constraint that all values to be inserted must be different from the others. Distinct results in the removal of the duplicate rows while retrieving data.
What’s the difference between unique and distinct in SQL?
The UNIQUE keyword in SQL plays the role of a database constraint; it ensures there are no duplicate values stored in a particular column or a set of columns. On the other hand, the DISTINCT keyword is used in the SELECT statement to fetch distinct rows from a table.
What is difference between distinct and all clauses?
If the ALL keyword is specified, duplicate rows are not removed from the query result. If the DISTINCT option is specified, all duplicate rows of data values are excluded from the query result. … The DISTINCT option keyword may only be used once in a SELECT clause.
What does distinct do in MySQL?
The MySQL DISTINCT clause is used to remove duplicates from the result set. The DISTINCT clause can only be used with SELECT statements.
What does the word distinct?
distinct, separate, discrete mean not being each and every one the same. distinct indicates that something is distinguished by the mind or eye as being apart or different from others. two distinct versions separate often stresses lack of connection or a difference in identity between two things.
What is difference between distinct?
Distinct and different are similar words, but they are not always used the same way. Distinct means “different in a way that you can see, hear, smell, feel, etc.” or “noticeably different.” Different means “not of the same kind” or “partly or totally unlike.”
Is unique function in SQL?
Unique constraint in SQL is used to check whether the sub query has duplicate tuples in it’s result. It returns a boolean value indicating the presence/absence of duplicate tuples. Unique construct returns true only if the sub query has no duplicate tuples, else it return false.
What does distinct mean in SQL?
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.
Should I use GROUP BY or distinct?
If you want to group your results, use GROUP BY, if you just want a unique list of a specific column, use DISTINCT.
Is GROUP BY or distinct faster?
GROUP BY is also faster than DISTINCT in AWS Redshift, because GROUP BY uses a XN HashAggregate and DISTINCT uses a XN Unique . It is the same problem that older versions of Postgres have.
Can we use distinct in HAVING clause?
The HAVING clause generally complements a GROUP BY clause. If you omit the GROUP BY clause, the HAVING clause applies to all rows that satisfy the query, and all rows in the table make up a single group. … The condition in the HAVING clause cannot include a DISTINCT or UNIQUE aggregate expression.