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SQL 4 begginers - NULL

SQL 4 begginers - NULL

When talking about values in database world there are three possible states. The three states are: there is a value, there is not a value (empty) and the value is NULL (unknown). Let's find out more about the NULL value....

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SQL 4 begginers - JOIN

SQL 4 begginers - JOIN

Let’s find out what is a JOIN and how to use it. The main difference between JOIN and UNION operator is that union combines results vertically, while the JOIN combines result's horizontally. There are different types of JOIN-s depending on the business need and we will discuss about them. Since the databases should be normalized it is essential to use joins to get details for some records....

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SQL 4 begginers - UNION

SQL 4 begginers - UNION

Let’s find out what is a UNION and what’s the difference between the UNION and the UNION ALL operators. The main difference between UNION and JOIN operator is that union combines results vertically. In simple words, the UNION operator returns results from two or more queries in one result set....

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