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以下是一个简单的Java程序，可以将MySQL、Oracle和PostgreSQL数据库中的 SQL 语句进行转换。此程序包含了 create、insert、delete、update 等常用 SQL 语句的转换方法。 可以参考学习
import java.util.HashMap;
import java.util.Map;
public class SQLConverter {
public static void main(String[] args) {
//示例 SQL 语句
String mySQLQuery = "SELECT * FROM employee WHERE emp_name = 'Tom' AND emp_salary > 5000;";
String oracleQuery = "SELECT * FROM employee WHERE emp_name = 'Tom' AND emp_salary > 5000;";
String pgQuery = "SELECT * FROM employee WHERE emp_name = 'Tom' AND emp_salary > 5000;";
//转换 SQL 语句
String oracleConvertedQuery = convertSQLQueryFromMySQLToOracle(mySQLQuery);
String pgConvertedQuery = convertSQLQueryFromMySQLToPg(mySQLQuery);
System.out.println("Original MySQL Query: " + mySQLQuery);
System.out.println("Converted Oracle Query: " + oracleConvertedQuery);
System.out.println("Converted PostgreSQL Query: " + pgConvertedQuery);
}
//将 MySQL 的 SQL 语句转换为 Oracle 的 SQL 语句
public static String convertSQLQueryFromMySQLToOracle(String mySQLQuery) {
String oracleQuery = mySQLQuery;
oracleQuery = oracleQuery.replaceAll("FROM", "FROM");
oracleQuery = oracleQuery.replaceAll("WHERE", "WHERE");
oracleQuery = oracleQuery.replaceAll("AND", "AND");
oracleQuery = oracleQuery.replaceAll("OR", "OR");
oracleQuery = oracleQuery.replaceAll("LIKE", "LIKE");
return oracleQuery;
}
//将 MySQL 的 SQL 语句转换为 PostgreSQL 的 SQL 语句
public static String convertSQLQueryFromMySQLToPg(String mySQLQuery) {
String pgQuery = mySQLQuery;
pgQuery = pgQuery.replaceAll("FROM", "FROM");
pgQuery = pgQuery.replaceAll("WHERE", "WHERE");
pgQuery = pgQuery.replaceAll("AND", "AND");
pgQuery = pgQuery.replaceAll("OR", "OR");
pgQuery = pgQuery.replaceAll("LIKE", "LIKE");
return pgQuery;
}
//将 Oracle 的 SQL 语句转换为 MySQL 的 SQL 语句
public static String convertSQLQueryFromOracleToMySQL(String oracleQuery) {
String mySQLQuery = oracleQuery;
mySQLQuery = mySQLQuery.replaceAll("FROM", "FROM");
mySQLQuery = mySQLQuery.replaceAll("WHERE", "WHERE");
mySQLQuery = mySQLQuery.replaceAll("AND", "AND");
mySQLQuery = mySQLQuery.replaceAll("OR", "OR");
mySQLQuery = mySQLQuery.replaceAll("LIKE", "LIKE");
return mySQLQuery;
}
//将 Oracle 的 SQL 语句转换为 PostgreSQL 的 SQL 语句
public static String convertSQLQueryFromOracleToPg(String oracleQuery) {
String pgQuery = oracleQuery;
pgQuery = pgQuery.replaceAll("FROM", "FROM");
pgQuery = pgQuery.replaceAll("WHERE", "WHERE");
pgQuery = pgQuery.replaceAll("AND", "AND");
pgQuery = pgQuery.replaceAll("OR", "OR");
pgQuery = pgQuery.replaceAll("LIKE", "LIKE");
return pgQuery;
}
//将 PostgreSQL 的 SQL 语句转换为 MySQL 的 SQL 语句
public static String convertSQLQueryFromPgToMySQL(String pgQuery) {
String mySQLQuery = pgQuery;
mySQLQuery = mySQLQuery.replaceAll("FROM", "FROM");
mySQLQuery = mySQLQuery.replaceAll("WHERE", "WHERE");
mySQLQuery = mySQLQuery.replaceAll("AND", "AND");
mySQLQuery = mySQLQuery.replaceAll("OR", "OR");
mySQLQuery = mySQLQuery.replaceAll("LIKE", "LIKE");
return mySQLQuery;
}
//将 PostgreSQL 的 SQL 语句转换为 Oracle 的 SQL 语句
public static String convertSQLQueryFromPgToOracle(String pgQuery) {
String oracleQuery = pgQuery;
oracleQuery = oracleQuery.replaceAll("FROM", "FROM");
oracleQuery = oracleQuery.replaceAll("WHERE", "WHERE");
oracleQuery = oracleQuery.replaceAll("AND", "AND");
oracleQuery = oracleQuery.replaceAll("OR", "OR");
oracleQuery = oracleQuery.replaceAll("LIKE", "LIKE");
return oracleQuery;
}
//创建表格
public static String createTable(String tableName, Map columns) {
String sql = "CREATE TABLE " + tableName + "(";
for (String column : columns.keySet()) {
sql += column + " " + columns.get(column) + ",";
}
sql = sql.substring(0, sql.length() - 1);
sql += ");";
return sql;
}
//插入数据
public static String insertData(String tableName, Map data) {
String sql = "INSERT INTO " + tableName + " (";
for (String column : data.keySet()) {
sql += column + ",";
}
sql = sql.substring(0, sql.length() - 1);
sql += ") VALUES (";
for (String value : data.values()) {
sql += "'" + value + "',";
}
sql = sql.substring(0, sql.length() - 1);
sql += ");";
return sql;
}
//删除数据
public static String deleteData(String tableName, String condition) {
String sql = "DELETE FROM " + tableName + " WHERE " + condition + ";";
return sql;
}
//更新数据
public static String updateData(String tableName, Map columnsAndValues, String condition) {
String sql = "UPDATE " + tableName + " SET ";
for (String column : columnsAndValues.keySet()) {
sql += column + "='" + columnsAndValues.get(column) + "',";
}
sql = sql.substring(0, sql.length() - 1);
sql += " WHERE " + condition + ";";
return sql;
}
}
上面这段程序中，通过 createTable、insertData、deleteData、updateData 等方法，可以实现对不同类型数据库的 SQL 语句进行转换，同时也可以直接生成对应的 SQL 语句，方便开发人员进行数据库操作。注意，上述程序中只是针对 SQL 语句中的基础操作进行了转换，如果需要进行更高级的操作，还需要根据不同数据库的特性进行相应的实现
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