in my MySQL schema, I have the category(id, parentid, name)
table
In the MSSQL, I have that CTE query (to build a category tree from the bottom up for a supplied category ID:
with CTE (id, pid, name) as ( select id, parentid as pid,name from category where id = 197 union all select CTE.pid as id , category.parentid as pid, category.name from CTE inner join category on category.id = CTE.pid ) select * from CTE
How to 'transform' that query to MySQL ?
Common Table Expression (CTE) is an important feature of MySQL that is used to generate a temporary result set. It can be used with any SQL statement like SELECT, INSERT, UPDATE, etc. The complicated queries can be simplified by using CTE.
You can use a common table expression (CTE) to simplify creating a view or table, selecting data, or inserting data. Use a CTE to create a table based on another table that you select using the CREATE TABLE AS SELECT (CTAS) clause.
Disadvantages of CTECTE's members cannot use the following clauses of keywords Distinct, Group By, Having, Top, Joins limiting by this type of the queries that can be created and reducing their complexity. The Recursive member can refer to the CTE only once.
A CTE provides better readability and also increases the performance as compared to the derived table. Unlike a derived table, a CTE is a subquery that can be self-referencing using its own name. It is also known as recursive CTE and can also be referenced multiple times in the same query.
Unfortunately MySQL doesn't support CTE (Common Table Expressions). This is long overdue IMO. Often, you can just use a subquery instead, but this particular CTE is recursive: it refers to itself inside the query. Recursive CTE's are extremely useful for hierarchical data, but again: MySql doesn't support them at all. You have to implement a stored procedure to get the same results.
A previous answer of mine should provide a good starting point:
Generating Depth based tree from Hierarchical Data in MySQL (no CTEs)
Thankfully it's not necessary anymore, as MySQL starting from 8.0.1 supports CTE.
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