framework/db/QueryBuilder.php
public function buildExistsCondition($operator, $operands, &$params)
    {
        array_unshift($operands, $operator);
        return $this->buildCondition($operands, $params);
    }
public function buildExistsCondition($operator, $operands, &$params)
    {
        array_unshift($operands, $operator);
        return $this->buildCondition($operands, $params);
    }
Creates an SQL expressions with the `EXISTS` operator.
@param string $operator the operator to use (e.g. `EXISTS` or `NOT EXISTS`)
@param array $operands contains only one element which is a [[Query]] object representing the sub-query.
@param array $params the binding parameters to be populated
@return string the generated SQL expression
@throws InvalidArgumentException if the operand is not a [[Query]] object.
@deprecated since 2.0.14. Use `buildCondition()` instead.