Can I use distinct in case statement SQL?
Can I use distinct in case statement SQL?
In general whenever we have to use ‘distinct’ clause along with case statement, it always resides outside the case statement unless we are using a sub-query in the case statement. If we put ‘distinct’ clause inside case statement, we will get ora-00936, missing expression error.
How do I count distinct occurrences in SQL?
To count the number of different values that are stored in a given column, you simply need to designate the column you pass in to the COUNT function as DISTINCT . When given a column, COUNT returns the number of values in that column. Combining this with DISTINCT returns only the number of unique (and non-NULL) values.
How do I count multiple distinct values in SQL?
SQL databases can work with tuples like values so you can just do: SELECT COUNT(DISTINCT (DocumentId, DocumentSessionId)) FROM DocumentOutputItems; If your database doesn’t support this, it can be simulated as per @oncel-umut-turer’s suggestion of CHECKSUM or other scalar function providing good uniqueness e.g. COUNT( …
Does Count distinct * Works in SQL?
As a simple example, let’s say you have two columns, A and B. There are three distinct A values, but only one distinct B value. It would be impossible for COUNT(DISTINCT *) to return a single, meaningful value. That is why that syntax cannot work.
Can we use multiple distinct in SQL?
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.
Is distinct or GROUP BY better?
Group by is expensive than Distinct since Group by does a sort on the result while distinct avoids it. But if you want to make group by yield the same result as distinct give order by null ..
How do I select distinct in SQL?
The SQL DISTINCT command used along with the SELECT keyword retrieves only unique data entries depending on the column list you have specified after it. To illustrate the usage of the DISTINCT keyword, we’ll use our Users table introduced in the previous chapters.
How do you count distinct values in SQL?
SQL COUNT(*) The purpose of SQL COUNT(*) is to count the number of lines returned by the SQL query. To count the number of rows in the revenues table, we use the following statement: select count(*) from revenues. You can put the keyword distinct followed by a column name inside the parenthesis instead of a star.
How to use count in SQL?
The SQL COUNT function is an aggregate function that returns the number of rows returned by a query. You can use the COUNT function in the SELECT statement to get the number of employees, the number of employees in each department, the number of employees who hold a specific job, etc. The following illustrates the syntax of the SQL COUNT function:
How to use distinct in SQL?
Example: Our database has a table named books with data in the columns author_firstname,author_lastname,and book_title.
