在Golang中建立动态（条件）WHERE SQL查询

Question

I'm using golang, go_reform, PostgreSQL. What i want to do is a REST search utility, and all went fine until I faced with conditional search query. "Conditional" here means I have 10 columns in a table to search in, and there may be ton of combinations so I can't handle them all separately. What i need is a query builder, but I have no understanding how can I implement this in Go. For now I have an idea like this, but it seems not really efficient

type Query struct {
    Id               *int64
    FirstName        *string
    MiddleName       *string
    LastName         *string
    AreaId           *int64
    Birthday         *time.Time
}

func (table *Query) Find() (*User) {
    if table.Id != nil {
        idstr := fmt.Sprintf("WHERE Id = %d AND ", table.Id)
    }
    else idstr := "WHERE "
    }
    if table.FirstName != "" {
        firststr := fmt.Sprintf("FirstName = %s AND", table.FirstName)
    }
    else firststr := ""
}//and so on

That feels really awkward so I'm wondering is there any better way to determine the fields that came to the Find() and build a SQL query based on this. (Actually it's coming in JSON and binding to Query struct, so maybe there is a way without struct). There also may be SQL workarounds, but I think it would be more efficient to build query without all possible columns.

EDIT: By the way, making my Google search query more accurate, i found a bunch of things related to my problem, probably i will try to use it now. For those who interested too: old go playground example

Making dynamic SQL queries to a MySQL DB

gorp package (snippets thing sounds very promising)

Answer 1

So, i found the solution. Big thanks to this guy, his code fits perfectly for me, love the way it works. Shame on guys who think that if-else boilerplate is the only way to make this possible. My exact code is this: Controller

func Find(c echo.Context) (err error) {
model := &models.Query{}
if err = c.Bind(model); err != nil {
    return c.JSON(http.StatusInternalServerError, u.Message(false, "Bad request"))
}
resp := model

.Find() return c.JSON(http.StatusOK, resp) Model function:

type Query map[string]interface{}

func (model Query) Find() (Query) {
    var values []interface{}
    var where []string
    for k, v := range model {
        values = append(values, v)
        //MySQL Way: where = append(where, fmt.Sprintf("%s = ?", k))
        where = append(where, fmt.Sprintf(`"%s" = %s`,k, "$" + strconv.Itoa(len(values))))
    }
    string := ("SELECT name FROM users WHERE " + strings.Join(where, " AND "))
    //for testing purposes i didn't ran actual query, just print it in the console and returned JSON back
    fmt.Println(string)
    return model

}

UPD: For PostgreSQL users like me (thanks to @mkopriva and his playground example), I'm able to have this placeholder thing working right on PostgreSQL