38. Functions in SQL

We’ve already seen aggregate functions in action:

SELECT COUNT(*) FROM users WHERE country = 'us' 

An aggregate function returns a value for the group of records. In our case, ☝ it gives us a number of records.

There’s another type of function in SQL – scalar functions. Unlike aggregate functions, they receive input (a column value, a user-defined value, like string/number or no input at all) and return a single value or a set of values. In the previous lesson, we saw a type-casting operator ::. In fact, it’s a shortcut of a CAST scalar function:

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-- Type your query here, for example this one -- lists all records from users table: SELECT * FROM users
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