How to Efficiently Insert or Update Records in MySQL Using IF EXISTS UPDATE ELSE INSERT INTO?

MySQL efficiently inserts or updates records: IF EXISTS UPDATE ELSE INSERT INTO

SQL provides several methods to insert or update records in a database table based on the existence of a unique key. This guide explains why what you tried doesn't work and provides two tested solutions using MySQL's INSERT ... ON DUPLICATE KEY UPDATE statement.

Why your attempt failed

• Missing unique constraint: Your query attempts to use ON DUPLICATE KEY UPDATE, but your subs_email column is missing a unique constraint, causing the query to fail.
• Syntax error: The IF EXISTS and BEGIN/END blocks you are trying to use are not valid SQL syntax for MySQL.

Solution 1: Create a unique constraint and use INSERT ... ON DUPLICATE KEY UPDATE

1. Make sure there is a unique constraint on the subs_email column:

ALTER TABLE subs ADD UNIQUE (subs_email);

2. Use the following query:

INSERT INTO subs (subs_name, subs_email, subs_birthday)
VALUES (?, ?, ?)
ON DUPLICATE KEY UPDATE
  subs_name     = VALUES(subs_name),
  subs_birthday = VALUES(subs_birthday);

Solution 2: Parameterized prepared statement using ON DUPLICATE KEY UPDATE

1. Prepare and execute statements using parameter placeholders:

String sql = "INSERT INTO subs (subs_name, subs_email, subs_birthday) VALUES (?, ?, ?)"
                    + " ON DUPLICATE KEY UPDATE subs_name = ?, subs_birthday = ?";

PreparedStatement preparedStatement = connection.prepareStatement(sql);
preparedStatement.setString(1, name);
preparedStatement.setString(2, email);
preparedStatement.setString(3, birthday);
preparedStatement.setString(4, name); // 重复键更新的第二个参数
preparedStatement.setString(5, birthday); // 重复键更新的第三个参数
preparedStatement.executeUpdate();

Remember to use parameter placeholders to prevent SQL injection attacks.

By applying these solutions, you can efficiently insert or update records in database tables based on the uniqueness of subs_email columns.

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