在Go中参数化SQL查询

Question

I have a simple query like the one below.

select json_agg(row_to_json(t)) from (select *                                                       
               from jobs, companies, locations                                                                                                                                                                                                                                 
               where jobs.company_id = companies.id and jobs.location_id = locations.id                                                                                                                                                                                        
               $extra                                                                                                                                                                                                                                                          
               and to_tsvector(jobs.name || ' ' || companies.name || ' ' || locations.name) @@ to_tsquery($1)                                                                                                                                                                  
               and to_tsvector(locations.name) @@ to_tsquery($2)                                                                                                                                                                                                               
               limit $3) t

But it has some problems regarding additional query. The $1 and $2 parameters is optional based on the query user requests. But still, at least in this case to_tsquery (postgresql) doesn't support any "match all" query like '*' so we must have the whole additional query and to_tsvector(locations.name) @@ to_tsquery($2) with proper parameter or not at all.

This makes building query based on parameter tiresome work since we have to copy same query and add additional query all the time, and it's easily add up. I have a solution in mind to use strings.Replace to add up additional queries, but still we need to escape the parameter if needed. Is there any other solution can get this done in a clean way ?

Answer 1

Here the tricky solution, hope this can help you. this query example using syntax query for github.com/lib/pq

baseQuery := `
        SELECT *
        FROM
            tableName
        WHERE
            (name ILIKE $1)`

params := []interface{}{"%" + nameLike + "%"}

// you can add optional criteria using this way
if condition==true {
        baseQuery += fmt.Sprintf(` AND student_no=$%d`, len(params)+1)
        params = append(params, studentNo)
}

filterQuery := baseQuery + ` ORDER BY contract_no ASC`

if totalLimit != 0 {
    filterQuery += fmt.Sprintf(` LIMIT $%d OFFSET $%d`, len(params)+1, len(params)+2)
    params = append(params, totalLimit, totalSkip)
}

rows, err := db.Query(filterQuery, params...)