SubQueryConverter (Apache Calcite API)

All Known Implementing Classes:

SqlToRelConverter.NoOpSubQueryConverter
```
public interface SubQueryConverter
```
SubQueryConverter provides the interface for classes that convert sub-queries into equivalent expressions.

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`boolean`	`canConvertSubQuery()`
`RexNode`	`convertSubQuery(SqlCall subQuery, SqlToRelConverter parentConverter, boolean isExists, boolean isExplain)`	Converts the sub-query to an equivalent expression.

- Method Detail
  - canConvertSubQuery
```
boolean canConvertSubQuery()
```
    Returns:
    
    Whether the sub-query can be converted
  - convertSubQuery
```
RexNode convertSubQuery(SqlCall subQuery,
                        SqlToRelConverter parentConverter,
                        boolean isExists,
                        boolean isExplain)
```
    Converts the sub-query to an equivalent expression.
    
    Parameters:
    
    subQuery - the SqlNode tree corresponding to a sub-query
    
    parentConverter - sqlToRelConverter of the parent query
    
    isExists - whether the sub-query is part of an EXISTS expression
    
    isExplain - whether the sub-query is part of an EXPLAIN PLAN statement
    
    Returns:
    
    the equivalent expression or null if the sub-query couldn't be converted