Ever felt confused by SQL's execution flow? ๐ค
Then you better stay with me!
Today let's exemplify SQL's execution order with a simple query๐๐ป
Then you better stay with me!
Today let's exemplify SQL's execution order with a simple query๐๐ป
1๏ธโฃ ๐ฆ๐ง๐๐ฅ๐ง๐๐ก๐ ๐๐ฅ๐ข๐ ๐ข๐จ๐ฅ ๐ฅ๐๐ช ๐ง๐๐๐๐
We use a dummy table with the salary of employees depending on their field and experience,
๐ฏ Our main goal?
Understand the field that earns the most.
We use a dummy table with the salary of employees depending on their field and experience,
๐ฏ Our main goal?
Understand the field that earns the most.
2๏ธโฃ ๐ฆ๐ค๐ ๐ค๐จ๐๐ฅ๐ฌ ๐ฆ๐ง๐ฅ๐จ๐๐ง๐จ๐ฅ๐ (to use)
We define a query to obtain our goal data.
We define a query to obtain our goal data.
3๏ธโฃ ๐ฆ๐ค๐ ๐๐ฆ ๐ ๐๐๐๐๐๐ฅ๐๐ง๐๐ฉ๐ ๐๐๐ก๐๐จ๐๐๐
SQL expects statements to be written in a specific orderโ...
but their evaluation sequence differs.
SQL expects statements to be written in a specific orderโ...
but their evaluation sequence differs.
๐ฆ๐ง๐๐ฃ 1 - ๐๐ฅ๐ข๐
First SQL determines the table where to take the data from.
In our case our dummy table salaries with all the info it contains.
First SQL determines the table where to take the data from.
In our case our dummy table salaries with all the info it contains.
๐ฆ๐ง๐๐ฃ 2 - ๐ช๐๐๐ฅ๐
Here data is filtered.
This is where we specify conditions to narrow down our results.
Think of it as our detective's magnifying glass! ๐
Here data is filtered.
This is where we specify conditions to narrow down our results.
Think of it as our detective's magnifying glass! ๐
๐ฆ๐ง๐๐ฃ 3 - ๐๐ฅ๐ข๐จ๐ฃ ๐๐ฌ
Grouping time!
This step clusters similar data together based on a specified column.
Perfect for summarizing data like employee fields! ๐
Grouping time!
This step clusters similar data together based on a specified column.
Perfect for summarizing data like employee fields! ๐
๐ฆ๐ง๐๐ฃ 4 - ๐๐๐ฉ๐๐ก๐
It's like WHERE's big sibling.
HAVING filters groups, especially useful after GROUP BY.
Only the groups meeting our criteria will pass this gate.
It's like WHERE's big sibling.
HAVING filters groups, especially useful after GROUP BY.
Only the groups meeting our criteria will pass this gate.
๐ฆ๐ง๐๐ฃ 5 - ๐ฆ๐๐๐๐๐ง
The star of the show!
Here we pick the columns we want to see in our final output.
Like an artist choosing colors for their painting ๐จ
The star of the show!
Here we pick the columns we want to see in our final output.
Like an artist choosing colors for their painting ๐จ
๐ฆ๐ง๐๐ฃ 6 - ๐ข๐ฅ๐๐๐ฅ ๐๐ฌ
Now we arrange our results.
This is where we decide the sorting order, like arranging books on a shelf. ๐
Now we arrange our results.
This is where we decide the sorting order, like arranging books on a shelf. ๐
๐ฆ๐ง๐๐ฃ 7 - ๐๐๐ ๐๐ง
The final touch!
Here we can limit the number of rows in our result set.
It's like picking the top 10 hits of the year. ๐
The final touch!
Here we can limit the number of rows in our result set.
It's like picking the top 10 hits of the year. ๐
4๏ธโฃ ๐๐๐ก๐๐ ๐ฅ๐๐ฆ๐จ๐๐ง
And voilร ....!
we have our neatly arranged and insightful data, ready for action!
Next week we will see how a JOIN command would affect this flow!
And voilร ....!
we have our neatly arranged and insightful data, ready for action!
Next week we will see how a JOIN command would affect this flow!
Still no clear how SQL's execution flow works?
Check my previous thread to further understand it! ๐๐ป
Check my previous thread to further understand it! ๐๐ป
https://twitter.com/739042635390816256/status/1737397055952204192
And that's all for now
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If you liked this thread, I am sharing Data Science and AI content.
So don't forget to follow me to get more content like this! (@rfeers)
RT the tweet below to help me share the word! :D
https://twitter.com/739042635390816256/status/1739962999182340445
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