To retrieve records that have a specific value based on a variable, you can use a tDBInput component with a context variable in the SQL query. A context variable is a variable that can store a value that can be changed at runtime or between different contexts. A context variable can be used in various components to parameterize their properties or expressions. A tDBInput component is used to read data from a database table by executing an SQL query. You can use a context variable in the SQL query to filter the records based on a dynamic value. For example, if you have a context variable named country that stores the value of the country you want to filter by, you can use it in the SQL query of the tDBInput component as follows:

SELECT id, address, country FROM customers WHERE country = ‘context.country’

This will retrieve only the records that have the same value as the context variable country in the country column.

You do not need to use a Run if trigger, a tMatchGroup component, or a tFilterColumns component to achieve this. A Run if trigger is used to execute a subjob conditionally based on a logical expression. A tMatchGroup component is used to group similar records based on matching rules and output them as master or duplicate records. A tFilterColumns component is used to select or remove columns from an input flow based on a list of column names. References: Talend Open Studio: Open-source ETL and Free Data Integration | Talend, [Contexts - 7.3], [tDBInput properties - 7.3], [Run if properties - 7.3], [tMatchGroup properties - 7.3], [tFilterColumns properties - 7.3]