我有一个java程序，可以通过任何类型的数据库查询任意数量的表。用户可以输入一个字符串，它将返回包含该字符串的表和行。问题是这些表中的一些有外键。在递交数据库之前，我怎么能递归地遍历查找外键和行而没有任何知识的所有表？
平台：Windows 7（64） 数据库类型：Postgres
代码：
public static void connectPostGres(String type, String server, String database, String port, String username, String password) {
System.out.println("-------- PostgreSQL JDBC Connection Testing ------------");
try {
Class.forName("org.postgresql.Driver");
} catch (ClassNotFoundException e) {
System.out.println("Where is your PostgreSQL JDBC Driver? Include in your library path!");
e.printStackTrace();
return;
}
System.out.println("PostgreSQL JDBC Driver Registered!");
Connection connection = null;
try {
connection = DriverManager.getConnection("jdbc:postgresql://" + server + ":" + port + "/" + database, username, password);
//connection = DriverManager.getConnection("*********);
} catch (SQLException e) {
System.out.println("doh!");
e.printStackTrace();
return;
}
if (connection != null) {
System.out.println("Searching...");
LinkedList allTables = new LinkedList();
try {
Statement st = connection.createStatement();
ResultSet rs = st.executeQuery("select * from pg_tables");//get all the tables
while (rs.next()) {
String myString = rs.getString("tablename");
if (myString.trim().charAt(0) == 'p' && myString.trim().charAt(1) == 'g') {
//this is just some crappy tables we dont want to query through
} else if (myString.trim().charAt(0) == 's' && myString.trim().charAt(1) == 'q' && myString.trim().charAt(2) == 'l') {
//this is just some crappy tables we dont want to query through
} else {
allTables.add(myString);//add all tables to a linkedlist
}
}
rs.close();
String masterQuery = "";
for (int i = 0; i columnList = new LinkedList();
for (int j = 1; j 0) {
for (int j = 0; j
答案 0 :(得分：1)
您可以阅读有关检索postgres元数据的信息article。
通常，您必须深入了解信息模式或使用系统目录。
修改
另外，将尽可能多的逻辑放入SQL中，以避免检索和处理根本不需要的数据。
这是来自上述文章的复制/粘贴，其中列出了所有约束（您可以在此处找到这两种方法）
SELECT c.conname AS constraint_name,
CASE c.contype
WHEN 'c' THEN 'CHECK'
WHEN 'f' THEN 'FOREIGN KEY'
WHEN 'p' THEN 'PRIMARY KEY'
WHEN 'u' THEN 'UNIQUE'
END AS "constraint_type",
CASE WHEN c.condeferrable = 'f' THEN 0 ELSE 1 END AS is_deferrable,
CASE WHEN c.condeferred = 'f' THEN 0 ELSE 1 END AS is_deferred,
t.relname AS table_name,
array_to_string(c.conkey, ' ') AS constraint_key,
CASE confupdtype
WHEN 'a' THEN 'NO ACTION'
WHEN 'r' THEN 'RESTRICT'
WHEN 'c' THEN 'CASCADE'
WHEN 'n' THEN 'SET NULL'
WHEN 'd' THEN 'SET DEFAULT'
END AS on_update,
CASE confdeltype
WHEN 'a' THEN 'NO ACTION'
WHEN 'r' THEN 'RESTRICT'
WHEN 'c' THEN 'CASCADE'
WHEN 'n' THEN 'SET NULL'
WHEN 'd' THEN 'SET DEFAULT'
END AS on_delete,
CASE confmatchtype
WHEN 'u' THEN 'UNSPECIFIED'
WHEN 'f' THEN 'FULL'
WHEN 'p' THEN 'PARTIAL'
END AS match_type,
t2.relname AS references_table,
array_to_string(c.confkey, ' ') AS fk_constraint_key
FROM pg_constraint c
LEFT JOIN pg_class t ON c.conrelid = t.oid
LEFT JOIN pg_class t2 ON c.confrelid = t2.oid
WHERE t.relname = 'testconstraints2'
AND c.conname = 'testconstraints_id_fk';
-- with INFORMATION_SCHEMA:
SELECT tc.constraint_name,
tc.constraint_type,
tc.table_name,
kcu.column_name,
tc.is_deferrable,
tc.initially_deferred,
rc.match_option AS match_type,
rc.update_rule AS on_update,
rc.delete_rule AS on_delete,
ccu.table_name AS references_table,
ccu.column_name AS references_field
FROM information_schema.table_constraints tc
LEFT JOIN information_schema.key_column_usage kcu
ON tc.constraint_catalog = kcu.constraint_catalog
AND tc.constraint_schema = kcu.constraint_schema
AND tc.constraint_name = kcu.constraint_name
LEFT JOIN information_schema.referential_constraints rc
ON tc.constraint_catalog = rc.constraint_catalog
AND tc.constraint_schema = rc.constraint_schema
AND tc.constraint_name = rc.constraint_name
LEFT JOIN information_schema.constraint_column_usage ccu
ON rc.unique_constraint_catalog = ccu.constraint_catalog
AND rc.unique_constraint_schema = ccu.constraint_schema
AND rc.unique_constraint_name = ccu.constraint_name
WHERE tc.table_name = 'testconstraints2'
AND tc.constraint_name = 'testconstraints_id_fk';
答案 1 :(得分：1)
您可以在DatabaseMetaData中查询此类信息：
public static void main(String[] args) throws Exception {
Connection connection = null;
try {
Class.forName(DRIVER);
connection = DriverManager.getConnection(URL, USERNAME, PASSWORD);
DatabaseMetaData metadata = connection.getMetaData();
ResultSet resultSet = metadata
.getExportedKeys(null, null, TABLE);
while (resultSet.next()) {
String pkTableName = resultSet.getString("PKTABLE_NAME");
String pkColName = resultSet.getString("PKCOLUMN_NAME");
String fkTableName = resultSet.getString("FKTABLE_NAME");
String fkColName = resultSet.getString("FKCOLUMN_NAME");
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
connection.close();
}
}