16 - Temp Tables in MySQL

16 - Temp Tables in MySQL

https://youtu.be/uEk07jXdKOo?si=jCd2G7sQ5MrN11KK

TOTAL: 7.46

-- Using Temporary Tables

-- Temporary tables are tables that are only visible to the session that created them.

-- They can be used to store intermediate results for complex queries or to manipulate data before inserting it into a permanent table.

-- Bang TAM nay khong ton tai trong database nhung van co the viet cau query thao tac duoc (tam chi tren file SQL khac - mien la dung tat APP)

-- There's 2 ways to create temp tables:

-- 1. This is the less commonly used way - which is to build it exactly like a real table and insert data into it

CREATE TEMPORARY TABLE temp_table

(first_name varchar(50),

last_name varchar(50),

favorite_movie varchar(100)

);

-- if we execute this it gets created and we can actualyl query it.

SELECT *

FROM temp_table;

-- notice that if we refresh out tables it isn't there. It isn't an actual table. It's just a table in memory.

-- now obviously it's balnk so we would need to insert data into it like this:

INSERT INTO temp_table

VALUES ('Alex','Freberg','Lord of the Rings: The Twin Towers');

-- now when we run it and execute it again we have our data

SELECT *

FROM temp_table;

-- the second way is much faster and my preferred method

-- 2. Build it by inserting data into it - easier and faster

CREATE TEMPORARY TABLE salary_over_50k

SELECT *

FROM employee_salary

WHERE salary > 50000;

-- if we run this query we get our output

SELECT *

FROM temp_table_2;

-- this is the primary way I've used temp tables especially if I'm just querying data and have some complex data I want to put into boxes or these temp tables to use later

-- it helps me kind of categorize and separate it out

-- In the next lesson we will look at the Temp Tables vs CTEs