Recursive cte postgresql

Non- recursive terthe non- recursive term is a CTE query definition that forms the base result set of the CTE structure. Evaluate the non- recursive term. For UNION (but not UNION ALL), discard duplicate rows. Include all remaining rows in the result of the recursive query, and also place them in a temporary working table.

Once the recursive CTE has been evaluate the of it can be used in the rest of the query like an ordinary CTE 3. Let’s walk through the example I gave above. First the recursive CTE evaluates the initial query which is just SELECT , and stores the , a single row with the value in the working table. The recursive member comes after a union all in the CTE definition.

Thir use the CTE like a table or view in the statement which can be a SELECT, INSERT, UPDATE, or DELETE. Let’s take some examples of using CTEs to get a better understanding. I have this working CTE example. PostgreSQL CTE examples.

I can select all grand-parents and all children. But how can I select all grand-parents and all children in one statement ? In this example I want Grandfather, Father, Son as output if I give Father as input. But I think this question should be standard SQL. Here’s a simple recursive CTE that generates the numbers to 10. The first time the recursive CTE runs it generates a single row using the anchor member.

In the second execution, the recursive member joins against the and outputs a second row, 2. In the third execution the recursive step joins against both rows and and adds the rows (a duplicate) and 3. It helps in breaking down complicated and large queries into simpler forms, which are easily readable. Preliminary: What is a Recursive Common Table Expression? An anchor part of a recursive CTE cannot be easily parametrized in a view. To work around this, we can wrap the CTE into a set-returning function which would accept. A Recursive CTE or Recursive Common Table Expression is a CTE that runs a query over each result of itself to generate an overall result.

This will allow you to generate a full list of hierarchical data, such as all employees and managers, or all product categories and their subcategories. What Does a Recursive CTE Look Like? It allows recursive CTE ’s to solve queries problems that would otherwise require the use of temporary tables, cursors, and other means. Recursive CTE ’s are well suited to querying hierarchical data, such as organization charts or production bill of materials, where each product’s components are made up of subcomponents, and so on. Let’s solve this particular problem using recursive queries.

In our case, that would be the top level questions and categories. I do not control the data or the columns. The data and table schema comes from an external source.

The table is growing continuously. Right now by about 30k records per day. Any node in the tree can be missing and they will be pulled from an external source at some point.