Database - 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

CREATE DATABASE permission denied in database ‘master’ (EF code-first)

Permission denied is a security so you need to add a “User” permission.. Right click you database(which is .mdf file) and then properties Go to security tab Click Continue button Click Add button Click Advance button Another window will show, then you click the “Find Now” button on the right side. On the fields below, … Read more

How to get size of mysql database?

Run this query and you’ll probably get what you’re looking for: This query comes from the mysql forums, where there are more comprehensive instructions available.

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

No more data to read from socket error

For errors like this you should involve oracle support. Unfortunately you do not mention what oracle release you are using. The error can be related to optimizer bind peeking. Depending on the oracle version different workarounds apply. You have two ways to address this: upgrade to 11.2 set oracle parameter _optim_peek_user_binds = false Of course underscore parameters … 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

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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