The CONNECT BY
clause determines the parent-child relationship of rows when performing a hierarchical query. The syntax of the CONNECT BY clause is as follows:
CONNECT BY { PRIOR parent_expr = child_expr |
child_expr = PRIOR parent_expr }
parent_expr
is evaluated on a candidate parent row. If parent_expr = child_expr
results in TRUE
for a row returned by the FROM
clause, this row is considered a child of the parent.
The following optional clauses can be specified in conjunction with the CONNECT BY
clause:
START WITH start_expression
The rows returned by the FROM
clause on which start_expression
evaluates to TRUE
become the root nodes of the hierarchy.
ORDER SIBLINGS BY expression [ ASC | DESC ] [, ...]
Sibling rows of the hierarchy are ordered by expression
in the result set.
Note PolarDB-O does not support the use of
AND
or other operators in the
CONNECT BY
clause.