1, wm_concat: the multiple rows of data returned is a summary, by dividing the data type is the default type CLOB
2, recursive queries (tree structure data query, such as menus, department, etc.)
SELECT
[The LEVEL], *
FEOM table_name
the START condition the WITH. 1
the CONNECT BY PRIOR is the condition 2
the WHERE condition. 3
the ORDER BY sort field
1 --- The conditions defining the root node, of course, can be relaxed authority, to obtain a plurality of root nodes, i.e. multiple trees acquired
condition 2 --- connection conditions, the purpose is what gives the relationship between the father and son, this relationship is recursive queries according to
condition 3 --- filter conditions, to filter all records returned by the
sort field --- sort all records returned
