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How does 'exists' affect output

I previously asked a question about how to organize a long search query. I have taken it apart. I am presently attempting to understand the function of some of its parts. Specifically, I am ...
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97 views

MS Access: adding column if not exist (or try/catch it)

this is an easy question, but I can't find out the solution... I have to check if a column exists and add it if the test is negative. How can I do with only sql code? This is the syntax for SQL ...
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106 views

Helpme undestand MDX exists function

After spend almost decade in OLTP world I got the courage to try to build my first CUBE. I installed VS2012 and created Business Intelligence -> Analysis Services. I did build Data Source Views, Cube ...
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1answer
33 views

Determine existence in recursive working table

I have a query that needs to check for existence of each input row type in another table, but it is unnecessary and inefficient to check for existence of subsequent rows of the same row type if one is ...
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52 views

How can I create a bool column for a view based on the result of a statement?

I'm using PostgreSQL as my database. CREATE TABLE groups ( id SERIAL NOT NULL, name TEXT NOT NULL, PRIMARY KEY (id), UNIQUE (name) ); CREATE TABLE users ( id ...
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782 views

Use if exists in postgresql [closed]

I know about the exists feature, but that does not help me with the given situation. What I want is: Check if some row exists, and if exists then check for an another row if row exists. Here's ...
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181 views

Performance of checking for data in related tables

NB: this question is purely academic / to help improve my understanding of SQL Server performance. Given a master table which relates to one or more other tables, how would you determine the best ...