Databricks Dashboards - How to use query parameter for a creating a dynamic query

Question

I am trying to create a dashboard with query parameter in a query for adding dynamic column names. here is the query

SELECT :column_names FROM table1

result of the query looks like this:

array(col1, col2, col3) 
["col1","col2","col3"]

I have tried exploding array

SELECT explode(:column_names) FROM table1

Result:

col
col1
col2
col3

I want to create a query like

SELECT col1, col2, col3 FROM table1

and the actual records from table in return. Is it possible to do it?

Answer 1

I have tried the below approach:

from pyspark.sql import SparkSession
from pyspark.sql.functions import col
spark = SparkSession.builder.appName("DynamicColumns").getOrCreate()
data = [(1, "a", "x"), (2, "b", "y"), (3, "c", "z")]
columns = ["col1", "col2", "col3"]
df = spark.createDataFrame(data, columns)
column_names = ["col1", "col2", "col3"]
selected_columns = [col(column) for column in column_names]
result_df = df.select(*selected_columns)
result_df.show()

Results:

+----+----+----+
|col1|col2|col3|
+----+----+----+
|   1|   a|   x|
|   2|   b|   y|
|   3|   c|   z|
+----+----+----+

In the above code I defined a list of column names to select dynamically. By using list comprehension to create a list of col() functions for each column name, I am able to dynamically select the desired columns from the DataFrame. Next, by passing the list of selected columns using the * operator to the select() function, able to generate a query that selects the specified columns from the DataFrame.