SQL Stuff

Subquery

A subquery is a query nested inside another SQL query, often used to retrieve data that will be used in the main query. It can return individual values or a set of results, helping to filter or modify the results of the outer query.

What does SUBSTR() do?

The SUBSTR() function extracts a substring from a string, starting at a specified position and continuing for a specified length.

What would SUBSTR(‘Trevor’, -1 ) return?

It returns the last character, 'r', from the string 'Trevor'.

REPLACE() is used to do what?

The REPLACE() function is used to replace occurrences of a specified substring within a string with another substring.

EXTRACT()

The EXTRACT() function is used to retrieve subparts, such as year, month, day, hour, etc., from a date or time value.

LEFT JOIN vs. LEFT OUTER JOIN

LEFT JOIN and LEFT OUTER JOIN mean the same thing.

Schema

collection of database structural elements such as tables, stored procedures, indexes, functions, and triggers.

Indexing

creates a special data structure that speeds up data retrieval by allowing the database to find rows more efficiently.

CASE Statement

way to implement the if-then-else logic in SQL.

OVER()

a window function that performs calculations across a specified range of rows related to the current row.

REGEX

Regular Expression

Used for pattern matching in SQL

REGEX