topic Re: Value of SQL variable in IF statement using Spark SQL in Data Engineering

Value of SQL variable in IF statement using Spark SQL

RicardoS — Fri, 11 Aug 2023 05:28:41 GMT

Hi there,

I am new to Spark SQL and would like to know if it possible to reproduce the below T-SQL query in Databricks. This is a sample query, but I want to determine if a query needs to be executed or not.

DECLARE @VariableA AS INT , @VariableB AS INT; SELECT @VariableA = COUNT(*) FROM [xxx].[TableExample] SELECT @VariableB = COUNT(*) + 1 FROM [xxx].[TableExample] IF (@VariableA = @VariableB) BEGIN PRINT 'Equal' END ELSE BEGIN PRINT 'Not equal' END

I want to use an IF statement to determine it. I already know how to set a variable using a SELECT statement:

SET VariableA = SELECT COUNT(*) FROM [xxx].[TableExample]; SET VariableB = SELECT COUNT(*) + 1 FROM [xxx].[TableExample];

Next I want to use VariableA and VariableB in an IF statement:

IF (${VariableA} = ${VariableB}, 'Equal', 'Not equal');

This is not working, because underwater this expression writes down the full SELECT statements of both variables instead of the results (numbers) to compare. When I write down only ${VariableA}; it gives me the correct result (number).

How can I make this work in the IF statement?

So to be clear, no PySpark solution, but SQL (Spark). Thank you!

Re: Value of SQL variable in IF statement using Spark SQL

Suman1985 — Sat, 12 Aug 2023 05:15:38 GMT

Hello , I read your question I just tell you that if you try following **bleep** ,

In Databricks, you can achieve similar conditional logic using Spark SQL. However, Spark SQL doesn't directly support variable assignment and manipulation in the same way as T-SQL. Instead, you would typically achieve your goal using DataFrames or SQL expressions. Here's how you can reproduce the logic you provided using Spark SQL:

-- Load the table as a DataFrame
val df = **bleep**.TableExample")

-- Calculate counts using DataFrames
val variableA = df.count()
val variableB = df.count() + 1

-- Use CASE WHEN for conditional logic
val result = spark.sql(
s"""
SELECT CASE WHEN $variableA = $variableB THEN 'Equal' ELSE 'Not equal' END AS result
"""
)

result.show()

****bleep** in a DataFrame.

Please note that Spark SQL does not directly support the use of variables like T-SQL does. Instead, you work with DataFrames and SQL expressions to achieve similar functionality. Myjdfaccount

I hope you like my answer Thank you i always try to give my best.

Best Regards,

Re: Value of SQL variable in IF statement using Spark SQL

RicardoS — Fri, 11 Aug 2023 10:48:37 GMT

Hi there,

Thank you for your response.

Using DataFrames and SQL expressions can still be done in a Spark SQL type of Notebook or is this already PySpark?

Thank you in advance!

Re: Value of SQL variable in IF statement using Spark SQL

Edthehead — Fri, 03 May 2024 14:54:38 GMT

Since you are looking for a single value back, you can use the CASE function to achieve what you need.

%sql

SET var.myvarA = (SELECT 6);

SET var.myvarB = (SELECT 7);

SELECT CASE WHEN ${var.myvarA} = ${var.myvarB} THEN 'Equal' ELSE 'Not equal' END AS result