数据库是什么数据库?
我先假设你是 Oracle 吧。
CREATE TABLE test_tree (
test_id INT NOT NULL,
pid INT,
test_val VARCHAR(10),
PRIMARY KEY (test_id)
);
INSERT INTO test_tree VALUES(1, NULL, '.NET');
INSERT INTO test_tree VALUES(2, 1, 'C#');
INSERT INTO test_tree VALUES(3, 1, 'J#');
INSERT INTO test_tree VALUES(4, 1, 'ASP.NET');
INSERT INTO test_tree VALUES(5, 1, 'VB.NET');
INSERT INTO test_tree VALUES(6, NULL, 'J2EE');
INSERT INTO test_tree VALUES(7, 6, 'EJB');
INSERT INTO test_tree VALUES(8, 6, 'Servlet');
INSERT INTO test_tree VALUES(9, 6, 'JSP');
INSERT INTO test_tree VALUES(10, NULL, 'Database');
INSERT INTO test_tree VALUES(11, 10, 'DB2');
INSERT INTO test_tree VALUES(12, 10, 'MySQL');
INSERT INTO test_tree VALUES(13, 10, 'Oracle');
INSERT INTO test_tree VALUES(14, 10, 'SQL Server');
INSERT INTO test_tree VALUES(15, 13, 'PL/SQL');
INSERT INTO test_tree VALUES(16, 15, 'Function');
INSERT INTO test_tree VALUES(17, 15, 'Procedure');
INSERT INTO test_tree VALUES(18, 15, 'Package');
INSERT INTO test_tree VALUES(19, 15, 'Cursor');
INSERT INTO test_tree VALUES(20, 14, 'T-SQL');
使用 START WITH CONNECT BY 语句实现树状查询
通过根节点 向下查询子节点
SELECT
LPAD(' ', 2*(LEVEL-1)) || test_val AS test_val
FROM
test_tree
START WITH
test_id IN (1, 6, 10)
CONNECT BY PRIOR test_id = pid;
TEST_VAL
-----------------------------------------------------------
.NET
C#
J#
ASP.NET
VB.NET
J2EE
EJB
Servlet
JSP
Database
DB2
TEST_VAL
-----------------------------------------------------------
MySQL
Oracle
PL/SQL
Function
Procedure
Package
Cursor
SQL Server
T-SQL
20 rows selected.
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