Recommended 10 commonly used digital assistants, welcome to download!

One day, a netizen in a circle on QQ sent a message asking for help: PropID name Amount3 Yuanbao 22 Le Dou 3 can be written as an output in a sql, which is to copy the number of entries corresponding to Amount: PropID name3 Yuanbao 3 Yuanbao 2 Le Bean 2 Le Dou 2 Le Dou [Note]: 3 Yuanbao 2 Note that the last column is 2, which means there are 2 such records

1. MySQL uses numeric auxiliary tables to implement complex Column changes to row

Introduction: After some research, use ordinary group by sum if case when and so on I couldn't figure it out, so I had to change my mind. I was stuck for a while, so I talked to the netizen Mr.W, and he provided the idea of ​​​​a digital auxiliary table.

2. Four classic sql programming problems

##Introduction: A numeric auxiliary table is a simple table containing only N integers from 1 to N, N is usually very large. The numeric auxiliary table is a very powerful tool, so we create a persistent numeric auxiliary table:

3. Four classic sql programming questions

Introduction: A numeric auxiliary table is a simple table containing only N integers from 1 to N, N is usually very large. The numeric auxiliary table is a very powerful tool, so we create a persistent numeric auxiliary table:

4. SqlServer 2005 T-SQL Query Study Notes (4)

Introduction: The author likes to build numerical auxiliary tables (that is, tables composed of 1-N numbers in order). Regarding how to build these auxiliary tables, he gave some Examples, these examples are very representative.

5. MySQL uses numeric auxiliary tables to implement complex column changes_MySQL

##Introduction: MySQL uses numeric auxiliary tables to implement complex column changes and rows

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