Talend: Query Database with Strings/Parameters already defined

Question

How can I perform a Query to my Database (using tOracleInput), like a Select, and use Strings that are already defined as parameters in other components, for example in a 'tFlowToIterate' ?

For example: "SELECT * from TABLE_X where FIELD_X= ? ;"

My '?' is the variable that comes from my tFlowToIterate component (foo). I already tried with (String)globalMap.get("foo"), and other similar forms...

Thanks

[Talend Open Studio for Data Integration v5.3.1; DB: Oracle]

Answer 1

You answered by yourself. tOracleInput component accepts the query as parameter. This is a very boring java String, no more, no less. This means that if you want to use a globalMap element inside a query, you just need to do a java String concatenation. Something like that:

"SELECT * from TABLE_X where FIELD_X='" + (String)globalMap.get("foo") + "'"

but this won't work (look carefully at the quotes):

"SELECT * from TABLE_X where FIELD_X='(String)globalMap.get("foo")'"

Keep in mind that if you write a query using string concatenation and external vars, the query editor will probably going to mess all the quotes, generating a broken query.

As a general advice, I never suggest to use the "*" operator inside a database input component like tOracleInput. Talend has a fixed-scheme structure that is generated at compile time. This means that if one day you'll add a column to TABLE_X, your ETL will going to fail.

A more robust solution is the following:

1. Write down your query with the * operator
2. Click "Guess Schema" to retrieve the table schema and put in your component metadata
3. Now click "Guess Query" to explicitely rewrite your SELECT
4. Fix the query (ie. WHERE conditions,...) if needed