dongqiaochi2711 2014-02-27 15:54
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使用数据库/ sql时如何获取返回的行数?

Given the following function:

func (me *OrderService) GetOrders(orderTx *sql.Tx, orderId int) (orders *sql.Rows) {
    orders, err := ecommTx.Query("SELECT * FROM orders WHERE id=?", orderId)
    if err != nil {
        log.Fatal(err)
    }
    log.Printf("Successfully queried and receive %d orders", orders.count)
    return orders
}

Are there any easy ways to .count the results? I'd like to keep this database engine agonistic, but FWIW.... I'm using Matt N's sqlite3 driver for my integration tests, but plan on having a different DB in prod.

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  • dpsyssiv90846 2014-03-03 04:52
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    sql.Query() returns *Rows. Rows is a reader, not a collection, so calls such as count() or len() etc. are not relevant. You have to read through Rows to know how many entries you've got:

    count := 0
    for orders.Next() {
        count++
    }
    
    log.Printf("Successfully queried and receive %d orders", count)
    

    You are not adding any extra overhead by doing so. Other languages, such as C# or Delphi, that might return a collection with a count property are simply doing the reading for you and packaging the results into a collection for your convenience.

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