Table with billion rows and 100 columns, can be represented with one short name. We can use the same logic and give a name to our SELECT statements. If we want to use those SELECT statements in a subquery, join or union, we can refer to them by their names. This is how we can reduce any complex statement to its building blocks. This will break complex logic to simple steps, where each step is easy to understand and manage.
CTEs are a way to name our SELECT statement, and then to use those names in the final SELECT, INSERT, DELETE , UPDATE or MERGE statement.
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Негізгі бет 0190 Common Table Expressions CTE in MonetDB
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