[英]Checking wether a MySQL table exists in a Java program using SQLException
[英]Java/Groovy and MySQL: Checking if row exists in table
我正在嘗試檢查包含兩個給定參數的表中是否存在特定行:record_id和ModifyDate。 到目前為止,我的代碼無法正常工作。
public void doSomething(int RECORD_ID) {
DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
Date date = new Date();
String modifiedDate = dateFormat.format(date);
Connection connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/db", "user", "pass");
Statement stmt = connection.createStatement();
String checkIfInDB = "select exists(select * from table where reference = ${RECORD_ID} and creation_date = '${modifiedDate}');"
ResultSet rs = stmt.executeQuery(checkIfInDB);
if(rs.next()) {
println "Query in db"
stmt.close();
connection.close();
return;
}
else {
String command = "INSERT INTO table(reference, creation_date) VALUES (${RECORD_ID}, '${modifiedDate}');"
stmt.executeUpdate(command)
println "Success"
stmt.close();
connection.close();
return;
}
}
如果用戶插入的RECORD_ID和日期已經存在,則程序應在打印“查詢數據庫”時將其添加到表中。 對於解決此問題的幫助,我將不勝感激。
我沒有列出所提供的代碼出了什么問題,而是提供了一個工作示例的示例,該示例可以用來幫助您進行工作...
public static void main(String[] args) {
int recordId = 1;
String jdbcSource = "jdbc:mysql://localhost:####/";
String user = "****";
String password = "****";
String checkIfInDB = "select count(*) as cnt from example_schema.example_table where example_table.reference = ? and example_table.creation_date = ?";
try (Connection connection = DriverManager.getConnection(jdbcSource, user, password)) {
PreparedStatement stmt = connection.prepareStatement(checkIfInDB);
stmt.setInt(1, recordId);
stmt.setDate(2, java.sql.Date.valueOf(LocalDate.now()));
ResultSet rs = stmt.executeQuery();
if (rs.next()) {
System.out.println("at least one row matched");
return;
} else {
// to-do implement insert statement
return;
}
} catch (SQLException e) {
e.printStackTrace();
}
}
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