import java.sql.Connection;
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import java.sql.DriverManager;
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import java.sql.ResultSet;
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import java.sql.ResultSetMetaData;
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import java.sql.Statement;
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/**
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* 只读探针：执行一条查询并把结果按列打印出来（用于核对服务器上的数据现状）。
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*
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* <p>用法：java Query <jdbc-url> "select ..."
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*/
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public class Query {
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public static void main(String[] args) throws Exception {
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try (Connection connection = DriverManager.getConnection(args[0], "root", "123456");
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Statement statement = connection.createStatement();
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ResultSet rows = statement.executeQuery(args[1])) {
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ResultSetMetaData meta = rows.getMetaData();
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int columns = meta.getColumnCount();
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StringBuilder header = new StringBuilder();
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for (int index = 1; index <= columns; index++) header.append(meta.getColumnLabel(index)).append(" | ");
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System.out.println(header);
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while (rows.next()) {
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StringBuilder line = new StringBuilder();
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for (int index = 1; index <= columns; index++) {
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Object value = rows.getObject(index);
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line.append(value == null ? "NULL" : String.valueOf(value)).append(" | ");
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}
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System.out.println(line);
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}
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}
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}
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}
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