How to compare the input data with the data in the database in java-mysql programming; If they are equal, it means that the data already exists and cannot be inserted.

Make a judgment before inserting into the database.

Boolean ifExists = false

String insertUser，strSql = " select user from emp

stmt . execute update(SQL)；

while( stmt.next){

if(insertuser . equals(stmt . getstring(" user ")){

ifExists = true

Break;

}

If (if it exists) (

System.out.println ("User already exists");

} Otherwise {

string SQL = " insert into EMP values(" "+num+" ')"； stmt . execute update(SQL)；

System.out.println ("Congratulations on joining successfully!" );

}