It is all about primary key
AND foreign key
. If you want to add a record with an id, that must exist in another table, it is a foreign key
.
If you don’t want this you can do the following:
conn = getConnection();
String query = "SELECT EXISTS(SELECT NULL FROM my_table WHERE number = ? LIMIT 1)";
pstmt = conn.prepareStatement(query);
pstmt.setString(1, myId); // Or setInt or whatever
rs = pstmt.executeQuery();
if (rs.next()) {
boolean exists= rs.getBoolean(1);
System.out.println("exists= " + exists);
} else {
System.out.println("error: could not get the record counts");
}
I edited my answer because, the query provided by: @eggyal is faster
solved How to check that there is a record in Database? [closed]