Create an String dynamically based on parameters

Question

I'm parametrizing a query in Scala.

I have an array of strings with column names named colNames.

I want to create an string where for each name of the string the output is A.colName = B.colName and then join all the items in the array putting an " AND " string between each item.

Example of input

val colNames = Array("colName1","colName2")
val table1 = "A"
val table2 = "B"

Example of the desired output

"A.colName1 = B.colName1 AND A.colName2 = B.colName2"

In a non FP language I would do that with a for loop, but I don't know how to do it in Scala in a functional way.

Are you using raw JDBC driver? How do you want to pair "A" with "colName1" and "B" with "colName2"? — Mateusz Kubuszok
– Mateusz Kubuszok, Commented Nov 21, 2022 at 11:49
@MateuszKubuszok I am passingg the raw query to the snowflake spark llibrary. A and B are the tables and i want to use them in a where condition where the columnName are equals — Fran Arenas
– Fran Arenas, Commented Nov 21, 2022 at 11:51
Then @Dogbert's answer should do the trick. (I wouldn't use infix notation though). — Mateusz Kubuszok
– Mateusz Kubuszok, Commented Nov 21, 2022 at 11:53
Whereever this piece of query ends up: make sure that the content of colNames is not controlled by the users, otherwise you'll quickly get requests along the lines of colNames = Array("colName1", "colName2 AND sendAllTehCoinzTo('BobbyTables') = 'success'"). — Andrey Tyukin
– Andrey Tyukin, Commented Nov 21, 2022 at 14:39

Dogbert · Accepted Answer · 2022-11-21 11:50:19Z

3

You can use the map and mkString methods on Array:

scala> colNames map { colName => s"${table1}.${colName} = ${table2}.${colName}" } mkString " AND "
val res0: String = A.colName1 = B.colName1 AND A.colName2 = B.colName2

answered Nov 21, 2022 at 11:50

Dogbert

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