| 摘要 |
Systems and methods are provided for performing a query in a distributed system. In one example, a query processor receives an instruction to perform a database operation involving a query. Based on an identification of a correlated subquery within the query, the query processor modifies the correlated subquery by replacing at least one correlated variable with a parameter or updatable constant. The modified subquery is sent to an external database for execution, where the external database is identified in the correlated subquery. The results of the modified subquery are received at the query processor from the external database and are used to execute the query. The correlated subquery includes a conditional relationship between a column in a first set of data and a column in a second set of data, wherein the first and second sets of data are stored in different external databases.
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