Example of calcite

Calcite-extract-Table-Where.java

package io.github.parj.sql;

import org.apache.calcite.config.Lex;
import org.apache.calcite.sql.*;
import org.apache.calcite.sql.fun.SqlStdOperatorTable;
import org.apache.calcite.sql.parser.SqlParseException;
import org.apache.calcite.sql.parser.SqlParser;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class App {
    public static void main(String[] args) {
        parseAndPrint("SELECT column1, column2 FROM table1 WHERE column1 = 42");
        parseAndPrint("SELECT column1 FROM table1 WHERE column2 IN (SELECT column2 FROM table2)");
        parseAndPrint("SELECT column1 FROM table1 UNION SELECT column1 FROM table2");
        parseAndPrint("SELECT t1.column1, t2.column2 FROM table1 t1 JOIN (SELECT column1 FROM table2) t2 ON t1.id = t2.id");
    }

    private static void parseAndPrint(String sqlQuery) {
        System.out.println("Parsing SQL Query: " + sqlQuery);

        SqlParser.Config parserConfig = SqlParser.config().withLex(Lex.JAVA);
        SqlParser sqlParser = SqlParser.create(sqlQuery, parserConfig);

        try {
            SqlNode sqlNode = sqlParser.parseQuery();
            handleSqlNode(sqlNode);
            System.out.println("-------------");
        } catch (SqlParseException e) {
            System.out.println("Error parsing query: " + e.getMessage());
            System.out.println("-------------");
        }
    }

    private static void handleSqlNode(SqlNode sqlNode) {
        SqlNodeHandler handler = HANDLERS.get(sqlNode.getClass());
        if (handler != null) {
            handler.handle(sqlNode);
        } else {
            System.out.println("Unsupported query type: " + sqlNode);
        }
    }

    interface SqlNodeHandler {
        void handle(SqlNode node);
    }

    static class SqlSelectHandler implements SqlNodeHandler {
        @Override
        public void handle(SqlNode node) {
            SqlSelect sqlSelect = (SqlSelect) node;
            System.out.println("Columns: " + sqlSelect.getSelectList());
            handleSqlNode(sqlSelect.getFrom());
        }
    }

    static class SqlBasicCallHandler implements SqlNodeHandler {
        @Override
        public void handle(SqlNode node) {
            SqlBasicCall sqlBasicCall = (SqlBasicCall) node;
            if (sqlBasicCall.getOperator() == SqlStdOperatorTable.AS) {
                System.out.println("Alias: " + sqlBasicCall.operand(1));
                handleSqlNode(sqlBasicCall.operand(0));
            } else if (sqlBasicCall.getOperator() == SqlStdOperatorTable.UNION) {
                System.out.println("UNION operation detected");
                for (SqlNode operand : sqlBasicCall.getOperandList()) {
                    handleSqlNode(operand);
                }
            } else {
                System.out.println("Unsupported operation: " + sqlBasicCall.getOperator());
            }
        }
    }

    static class SqlIdentifierHandler implements SqlNodeHandler {
        @Override
        public void handle(SqlNode node) {
            SqlIdentifier sqlIdentifier = (SqlIdentifier) node;
            List<String> names = sqlIdentifier.names;
            if (names.size() > 1) {
                System.out.println("Table: " + names.get(0));
                System.out.println("Alias: " + names.get(names.size() - 1));
            } else {
                System.out.println("Table: " + names.get(0));
            }
        }
    }

    static class SqlJoinHandler implements SqlNodeHandler {
        @Override
        public void handle(SqlNode node) {
            SqlJoin sqlJoin = (SqlJoin) node;
            System.out.println("Join detected");
            handleSqlNode(sqlJoin.getLeft());
            handleSqlNode(sqlJoin.getRight());
        }
    }

    private static final Map<Class<? extends SqlNode>, SqlNodeHandler> HANDLERS = new HashMap<>();
    static {
        HANDLERS.put(SqlSelect.class, new SqlSelectHandler());
        HANDLERS.put(SqlBasicCall.class, new SqlBasicCallHandler());
        HANDLERS.put(SqlIdentifier.class, new SqlIdentifierHandler());
        HANDLERS.put(SqlJoin.class, new SqlJoinHandler());
    }
}