sql - Read For Learn

What is the difference between Scope_Identity(), Identity(), @@Identity, and Ident_Current()?

The @@identity function returns the last identity created in the same session. The scope_identity() function returns the last identity created in the same session and the same scope. The ident_current(name) returns the last identity created for a specific table or view in any session. The identity() function is not used to get an identity, it’s used to create an identity in a select…into query. The … Read more

Query error with ambiguous column name in SQL

We face this error when we are selecting data from more than one tables by joining tables and at least one of the selected columns (it will also happen when use * to select all columns) exist with same name in more than one tables (our selected/joined tables). In that case we must have to specify from which table we are … Read more

Warning: Null value is eliminated by an aggregate or other SET operation in Aqua Data Studio

You would mostly be using COUNT to summarize over a UID. Therefore COUNT([uid]) will produce the warning: Warning: Null value is eliminated by an aggregate or other SET operation. whilst being used with a left join, where the counted object does not exist. Using COUNT(*) in this case would also render incorrect results, as you would then be counting the … Read more

What does the following Oracle error mean: invalid column index

If that’s a SQLException thrown by Java, it’s most likely because you are trying to get or set a value from a ResultSet, but the index you are using isn’t within the range. For example, you might be trying to get the column at index 3 from the result set, but you only have two … Read more

ORA-00972 identifier is too long alias column name

No, prior to Oracle version 12.2, identifiers are not allowed to exceed 30 characters in length. See the Oracle SQL Language Reference. However, from version 12.2 they can be up to 128 bytes long. (Note: bytes, not characters).

How to join two tables by multiple columns in SQL?

Yes: You can use Inner Join to join on multiple columns. Create table Insert values

Get day of week in SQL Server 2005/2008

Use DATENAME or DATEPART:

Column ‘user_id’ in field list is ambiguous

It means that both tables in the query have the column user_id. You need to specify which one you want to get in the SELECT statement like SELECT username, image, re.user_id

PDO with INSERT INTO through prepared statements

You should be using it like so Prepared statements are used to sanitize your input, and to do that you can use :foo without any single quotes within the SQL to bind variables, and then in the execute() function you pass in an associative array of the variables you defined in the SQL statement. You may also use ? instead of :foo and then pass in … Read more

SQL join on multiple columns in same tables

I have 2 subqueries, but I’m having trouble joining columns together from the same tables. I tried: If I simply end the query with ON a.userid = b.sourceid it works, but how can I also join these tables on another column also ON a.listid = b.destinationid ?? Any help appreciated.

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