如何使用JDBC在Apache Derby数据库中删除模式中的所有表格？
11个回答
7
感谢这篇博客：
步骤1：
运行SQL语句，但不要忘记在下面两个位置中将模式名称“APP”替换为您的模式名称：
SELECT
'ALTER TABLE '||S.SCHEMANAME||'.'||T.TABLENAME||' DROP CONSTRAINT '||C.CONSTRAINTNAME||';'
FROM
SYS.SYSCONSTRAINTS C,
SYS.SYSSCHEMAS S,
SYS.SYSTABLES T
WHERE
C.SCHEMAID = S.SCHEMAID
AND
C.TABLEID = T.TABLEID
AND
S.SCHEMANAME = 'APP'
UNION
SELECT 'DROP TABLE ' || schemaname ||'.' || tablename || ';'
FROM SYS.SYSTABLES
INNER JOIN SYS.SYSSCHEMAS ON SYS.SYSTABLES.SCHEMAID = SYS.SYSSCHEMAS.SCHEMAID
where schemaname='APP';
第二步：
以上执行的结果是一组SQL语句，将它们复制到SQL编辑器中，执行它们，然后约束和表将被删除。
- Sym-Sym
5
要实际执行此操作的代码，请查看Derby分发版的Derby测试套件部分中的CleanDatabaseTestSetup.java。
- Bryan Pendleton
2
1你可能正在寻找http://svn.apache.org/viewvc/db/derby/code/trunk/java/testing/org/apache/derbyTesting/junit/JDBC.java?revision=990292&view=markup -- 这个文件包含了实际的dropSchema()方法，它可以删除单个数据库（而不是给定连接中的所有用户数据库）。 - tucuxi
我编辑了我的答案，以更正Derby 10.15后源代码新布局的链接位置。此外，先前评论中的链接也存在相同的问题，现在应该是http://svn.apache.org/viewvc/db/derby/code/trunk/java/org.apache.derby.tests/org/apache/derbyTesting/junit/JDBC.java?view=markup。 - Bryan Pendleton
3
在Java中编写一个简单的方法，其中执行一个
DROP TABLE [tablename]
参数传递tablename。
另一种方法是通过循环查询形成的记录集。
SELECT tablename FROM SYSTABLES
调用第一个方法。
- Telcontar
1
应该有一定的删除顺序。 - Clark Bao
1
我认为大多数数据库提供商不允许使用DROP TABLE *（或类似语句）。
我认为最好的方法是使用SHOW TABLES，然后通过结果集循环遍历每个表并进行删除操作。
希望对你有所帮助。
- graham.reeds
0
对于那些想要以编程方式删除所有模式而不必每次手动复制粘贴 SQL 的人，这里是从 org.apache.derbyTesting.junit.CleanDatabaseTestSetup 和 org.apache.derbyTesting.junit.JDBC 中提取的代码。您只需调用 dropAllSchemas(connection); 即可。
public static void dropAllSchemas(Connection conn) throws SQLException {
DatabaseMetaData dmd = conn.getMetaData();
SQLException sqle = null;
// Loop a number of arbitary times to catch cases
// where objects are dependent on objects in
// different schemas.
for (int count = 0; count < 5; count++) {
// Fetch all the user schemas into a list
List<String> schemas = new ArrayList<String>();
ResultSet rs = dmd.getSchemas();
while (rs.next()) {
String schema = rs.getString("TABLE_SCHEM");
if (schema.startsWith("SYS"))
continue;
if (schema.equals("SQLJ"))
continue;
if (schema.equals("NULLID"))
continue;
schemas.add(schema);
}
rs.close();
// DROP all the user schemas.
sqle = null;
for (String schema : schemas) {
try {
dropSchema(dmd, schema);
} catch (SQLException e) {
sqle = e;
}
}
// No errors means all the schemas we wanted to
// drop were dropped, so nothing more to do.
if (sqle == null)
return;
}
throw sqle;
}
/**
* Constant to pass to DatabaseMetaData.getTables() to fetch
* just tables.
*/
public static final String[] GET_TABLES_TABLE = new String[] {"TABLE"};
/**
* Constant to pass to DatabaseMetaData.getTables() to fetch
* just views.
*/
public static final String[] GET_TABLES_VIEW = new String[] {"VIEW"};
/**
* Constant to pass to DatabaseMetaData.getTables() to fetch
* just synonyms.
*/
public static final String[] GET_TABLES_SYNONYM =
new String[] {"SYNONYM"};
/**
* Drop a database schema by dropping all objects in it
* and then executing DROP SCHEMA. If the schema is
* APP it is cleaned but DROP SCHEMA is not executed.
*
* TODO: Handle dependencies by looping in some intelligent
* way until everything can be dropped.
*
*
* @param dmd DatabaseMetaData object for database
* @param schema Name of the schema
* @throws SQLException database error
*/
public static void dropSchema(DatabaseMetaData dmd, String schema) throws SQLException{
Connection conn = dmd.getConnection();
Statement s = dmd.getConnection().createStatement();
// Triggers
PreparedStatement pstr = conn.prepareStatement(
"SELECT TRIGGERNAME FROM SYS.SYSSCHEMAS S, SYS.SYSTRIGGERS T "
+ "WHERE S.SCHEMAID = T.SCHEMAID AND SCHEMANAME = ?");
pstr.setString(1, schema);
ResultSet trrs = pstr.executeQuery();
while (trrs.next()) {
String trigger = trrs.getString(1);
s.execute("DROP TRIGGER " + escape(schema, trigger));
}
trrs.close();
pstr.close();
// Functions - not supported by JDBC meta data until JDBC 4
// Need to use the CHAR() function on A.ALIASTYPE
// so that the compare will work in any schema.
PreparedStatement psf = conn.prepareStatement(
"SELECT ALIAS FROM SYS.SYSALIASES A, SYS.SYSSCHEMAS S" +
" WHERE A.SCHEMAID = S.SCHEMAID " +
" AND CHAR(A.ALIASTYPE) = ? " +
" AND S.SCHEMANAME = ?");
psf.setString(1, "F" );
psf.setString(2, schema);
ResultSet rs = psf.executeQuery();
dropUsingDMD(s, rs, schema, "ALIAS", "FUNCTION");
// Procedures
rs = dmd.getProcedures((String) null,
schema, (String) null);
dropUsingDMD(s, rs, schema, "PROCEDURE_NAME", "PROCEDURE");
// Views
rs = dmd.getTables((String) null, schema, (String) null,
GET_TABLES_VIEW);
dropUsingDMD(s, rs, schema, "TABLE_NAME", "VIEW");
// Tables
rs = dmd.getTables((String) null, schema, (String) null,
GET_TABLES_TABLE);
dropUsingDMD(s, rs, schema, "TABLE_NAME", "TABLE");
// At this point there may be tables left due to
// foreign key constraints leading to a dependency loop.
// Drop any constraints that remain and then drop the tables.
// If there are no tables then this should be a quick no-op.
ResultSet table_rs = dmd.getTables((String) null, schema, (String) null,
GET_TABLES_TABLE);
while (table_rs.next()) {
String tablename = table_rs.getString("TABLE_NAME");
rs = dmd.getExportedKeys((String) null, schema, tablename);
while (rs.next()) {
short keyPosition = rs.getShort("KEY_SEQ");
if (keyPosition != 1)
continue;
String fkName = rs.getString("FK_NAME");
// No name, probably can't happen but couldn't drop it anyway.
if (fkName == null)
continue;
String fkSchema = rs.getString("FKTABLE_SCHEM");
String fkTable = rs.getString("FKTABLE_NAME");
String ddl = "ALTER TABLE " +
escape(fkSchema, fkTable) +
" DROP FOREIGN KEY " +
escape(fkName);
s.executeUpdate(ddl);
}
rs.close();
}
table_rs.close();
conn.commit();
// Tables (again)
rs = dmd.getTables((String) null, schema, (String) null,
GET_TABLES_TABLE);
dropUsingDMD(s, rs, schema, "TABLE_NAME", "TABLE");
// drop UDTs
psf.setString(1, "A" );
psf.setString(2, schema);
rs = psf.executeQuery();
dropUsingDMD(s, rs, schema, "ALIAS", "TYPE");
// drop aggregates
psf.setString(1, "G" );
psf.setString(2, schema);
rs = psf.executeQuery();
dropUsingDMD(s, rs, schema, "ALIAS", "DERBY AGGREGATE");
psf.close();
// Synonyms - need work around for DERBY-1790 where
// passing a table type of SYNONYM fails.
rs = dmd.getTables((String) null, schema, (String) null,
GET_TABLES_SYNONYM);
dropUsingDMD(s, rs, schema, "TABLE_NAME", "SYNONYM");
// sequences
if ( sysSequencesExists( conn ) )
{
psf = conn.prepareStatement
(
"SELECT SEQUENCENAME FROM SYS.SYSSEQUENCES A, SYS.SYSSCHEMAS S" +
" WHERE A.SCHEMAID = S.SCHEMAID " +
" AND S.SCHEMANAME = ?");
psf.setString(1, schema);
rs = psf.executeQuery();
dropUsingDMD(s, rs, schema, "SEQUENCENAME", "SEQUENCE");
psf.close();
}
// Finally drop the schema if it is not APP
if (!schema.equals("APP")) {
s.executeUpdate("DROP SCHEMA " + escape(schema) + " RESTRICT");
}
conn.commit();
s.close();
}
/**
* Return true if the SYSSEQUENCES table exists.
*/
private static boolean sysSequencesExists( Connection conn ) throws SQLException
{
PreparedStatement ps = null;
ResultSet rs = null;
try {
ps = conn.prepareStatement
(
"select count(*) from sys.systables t, sys.sysschemas s\n" +
"where t.schemaid = s.schemaid\n" +
"and ( cast(s.schemaname as varchar(128)))= 'SYS'\n" +
"and ( cast(t.tablename as varchar(128))) = 'SYSSEQUENCES'" );
rs = ps.executeQuery();
rs.next();
return ( rs.getInt( 1 ) > 0 );
}
finally
{
if ( rs != null ) { rs.close(); }
if ( ps != null ) { ps.close(); }
}
}
/**
* Escape a non-qualified name so that it is suitable
* for use in a SQL query executed by JDBC.
*/
public static String escape(String name)
{
StringBuffer buffer = new StringBuffer(name.length() + 2);
buffer.append('"');
for (int i = 0; i < name.length(); i++) {
char c = name.charAt(i);
// escape double quote characters with an extra double quote
if (c == '"') buffer.append('"');
buffer.append(c);
}
buffer.append('"');
return buffer.toString();
}
/**
* Escape a schema-qualified name so that it is suitable
* for use in a SQL query executed by JDBC.
*/
public static String escape(String schema, String name)
{
return escape(schema) + "." + escape(name);
}
/**
* DROP a set of objects based upon a ResultSet from a
* DatabaseMetaData call.
*
* TODO: Handle errors to ensure all objects are dropped,
* probably requires interaction with its caller.
*
* @param s Statement object used to execute the DROP commands.
* @param rs DatabaseMetaData ResultSet
* @param schema Schema the objects are contained in
* @param mdColumn The column name used to extract the object's
* name from rs
* @param dropType The keyword to use after DROP in the SQL statement
* @throws SQLException database errors.
*/
private static void dropUsingDMD(
Statement s, ResultSet rs, String schema,
String mdColumn,
String dropType) throws SQLException
{
String dropLeadIn = "DROP " + dropType + " ";
// First collect the set of DROP SQL statements.
ArrayList<String> ddl = new ArrayList<String>();
while (rs.next())
{
String objectName = rs.getString(mdColumn);
String raw = dropLeadIn + escape(schema, objectName);
if (
"TYPE".equals( dropType ) ||
"SEQUENCE".equals( dropType ) ||
"DERBY AGGREGATE".equals( dropType )
)
{ raw = raw + " restrict "; }
ddl.add( raw );
}
rs.close();
if (ddl.isEmpty())
return;
// Execute them as a complete batch, hoping they will all succeed.
s.clearBatch();
int batchCount = 0;
for (Iterator i = ddl.iterator(); i.hasNext(); )
{
Object sql = i.next();
if (sql != null) {
s.addBatch(sql.toString());
batchCount++;
}
}
int[] results;
boolean hadError;
try {
results = s.executeBatch();
//Assert.assertNotNull(results);
//Assert.assertEquals("Incorrect result length from executeBatch", batchCount, results.length);
hadError = false;
} catch (BatchUpdateException batchException) {
results = batchException.getUpdateCounts();
//Assert.assertNotNull(results);
//Assert.assertTrue("Too many results in BatchUpdateException", results.length <= batchCount);
hadError = true;
}
// Remove any statements from the list that succeeded.
boolean didDrop = false;
for (int i = 0; i < results.length; i++)
{
int result = results[i];
if (result == Statement.EXECUTE_FAILED)
hadError = true;
else if (result == Statement.SUCCESS_NO_INFO || result >= 0) {
didDrop = true;
ddl.set(i, null);
}
//else
//Assert.fail("Negative executeBatch status");
}
s.clearBatch();
if (didDrop) {
// Commit any work we did do.
s.getConnection().commit();
}
// If we had failures drop them as individual statements
// until there are none left or none succeed. We need to
// do this because the batch processing stops at the first
// error. This copes with the simple case where there
// are objects of the same type that depend on each other
// and a different drop order will allow all or most
// to be dropped.
if (hadError) {
do {
hadError = false;
didDrop = false;
for (ListIterator<String> i = ddl.listIterator(); i.hasNext();) {
String sql = i.next();
if (sql != null) {
try {
s.executeUpdate(sql);
i.set(null);
didDrop = true;
} catch (SQLException e) {
hadError = true;
}
}
}
if (didDrop)
s.getConnection().commit();
} while (hadError && didDrop);
}
}
附注：这段代码在我将数据库从支持DROP ALL OBJECTS的H2迁移到不支持该功能的Apache Derby时非常有用（头疼）。我迁移离开H2的唯一原因是它是一个完全的内存数据库，而我的服务器RAM已经不够用了，所以我决定尝试一下Apache Derby。H2比Derby更容易使用和更用户友好，我强烈推荐使用它。我很遗憾不能负担继续使用H2所需的RAM。 顺便说一句，对于那些受到Derby缺乏LIMIT或UPSERT影响的人，请参阅此帖子，了解如何使用FETCH NEXT代替LIMIT，以及正确使用MERGE INTO的方法。
- keithphw
0
从http://squirrel-sql.sourceforge.net/下载Squirrel SQL。
连接到数据库。
展开TABLE节点。
选择要删除的表。
右键单击并选择->脚本->删除表脚本
运行生成的查询
您甚至可以选择删除记录以清空所选表。
- Brij
0
一个简单的解决方案是右键单击 -> 断开连接，然后删除包含您的数据库的文件夹并重新连接。
- Ben
0
JDBC 允许您以与数据库无关的方式解决任务：
- 打开连接
- 获取 DatabaseMetaData
- 使用它列出数据库中的所有表 JavaDoc
- 遍历结果集并为每个表触发 DROP TABLE
- Thomas Morgner
0
- 你必须从Derby DB系统目录中生成模式和表名。
- 按关系对所有表进行排序。
- 为删除所有表生成Java语句。
- 使用autoCommit()方法并将此方法设置为false，以便在出现错误时手动提交或回滚事务。
- 运行你的Java进程。 祝你好运。
- Fuangwith S.
0
一个更简单的解决方案是使用JDBC运行"drop database foo"然后"create database foo"。但是，这将导致数据库中的所有对象都被删除（即不仅仅是表）。
- Don
网页内容由stack overflow 提供, 点击上面的可以查看英文原文，
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