为什么从数据库中删除某些数据后，它不会插入同一表

I have faced a strange issue, after deleting data from one table it is impossible to insert into the table again.

here is an example

I am using postgres DB

_, err = con.Query(`
    DELETE FROM loan_aims WHERE _loan = $1;
`, input.ID)
if err != nil {
    tx.Rollback()
    log.Println(err)
    return false, fmt.Errorf("can not delete additional data from loan_aims")
}

   stmtAim, err := con.Prepare(`INSERT INTO loan_aims(_loan,_aim) VALUES ($1,$2)`)
if err != nil {
    tx.Rollback()
    log.Println(err)
    return false, fmt.Errorf("can not insert into loan_aims")
}

 for i := 0; i < len(aims); i++ {
    _, err := stmtAim.Exec(loanID, aims[i])

    if err != nil {
        tx.Rollback()
        return false, fmt.Errorf("can not insert aim 2")
    }
} 

I have tried to remove this

_, err = con.Query(`
    DELETE FROM loan_aims WHERE _loan = $1;
`, input.ID)
if err != nil {
    tx.Rollback()
    log.Println(err)
    return false, fmt.Errorf("can not delete additional data from loan_aims")
}

and it works just fine

Typically, you should use db.Exec() for DELETE.

_, err = db.Exec("delete from foo")
if err != nil {
    log.Fatal(err)
}