AMC certification: SQL pre-assessment

SQL 배경 지식이 요구되는 AMC 관련 코스를 듣는 중인데 내가 아는 거라곤 셀렉트 프롬 웨어가 전부라.. 프리어세스먼트에 나온 내용이라두 익혀두고자 적어봄

JOIN vs. UNION

- Inner / Right / Let / Full Outer Join

https://www.sqlshack.com/a-step-by-step-walkthrough-of-sql-inner-join/

A step-by-step walkthrough of SQL Inner Join

https://www.w3schools.com/sql/sql_join.asp#:~:text=LEFT%20(OUTER)%20JOIN%20%3A%20Returns,either%20left%20or%20right%20table

SQL Joins

https://www.scaler.com/topics/sql-union-vs-join/

What's the Difference between JOIN and UNION in SQL? - Scaler Topics

 

CAST function: The SQL CAST function converts the data type of an expression to the specified data type

https://docs.intersystems.com/irislatest/csp/docbook/DocBook.UI.Page.cls?KEY=RSQL_cast#:~:text=The%20SQL%20CAST%20function%20converts,is%20more%20flexible%20than%20CAST

CAST | InterSystems IRIS Data Platform 2023.2

 

CASE function: The CASE statement goes through conditions and return a value when the first condition is met (like an IF-THEN-ELSE statement).

https://www.w3schools.com/sql/func_mysql_case.asp#:~:text=The%20CASE%20statement%20goes%20through,value%20in%20the%20ELSE%20clause

MySQL CASE Function

 

PARTITION BY: We use SQL PARTITION BY to divide the result set into partitions and perform computation on each subset of partitioned data.

https://www.sqlshack.com/sql-partition-by-clause-overview/

SQL PARTITION BY Clause overview

 

ORDER BY: The ORDER BY keyword is used to sort the result-set in ascending or descending order.

https://www.w3schools.com/sql/sql_orderby.asp#:~:text=The%20SQL%20ORDER%20BY%20Keyword,order%2C%20use%20the%20DESC%20keyword

SQL ORDER BY Keyword

 

CTE: A Common Table Expression (CTE) is the result set of a query which exists temporarily and for use only within the context of a larger query.

https://chartio.com/resources/tutorials/using-common-table-expressions/#:~:text=A%20Common%20Table%20Expression%20(CTE,the%20duration%20of%20the%20query

Common Table Expressions: When and How to Use Them