How to group Postgres data correctly - postgresql

Question

In PostgreSQL, I have such table:
| QUESTION_TEXT | CATEGORY | AGREE_PERCENT | DISAGREE_PERCENT |
|----------------------------------------|----------|---------------|------------------|
| Do you support the President's policy? | Policy | 50 | 50 |
| Do you support Democrats? | Policy | 32 | 68 |
| Do you support the Lannisters? | Cinema | 45 | 55 |
| Do you support Spielberg's work? | Cinema | 60 | 40 |
In my Go application with the help of gorm library I make SQL request to PostgreSQL database like that:
type Entry struct {
QuestionText string `json:"question_text"`
Category string `json:"category"`
AgreePercent float64 `json:"agree_percent"`
DisagreePercent float64 `json:"disagree_percent"`
}
rows, _ := database.DBGORM.Raw("SELECT * FROM SPECIFICATION").Rows()
for rows.Next() {
entry := &Entry{}
if err = rows.Scan(&entry.QuestionText, & entry.Category, &entry.AgreePercent, &entry.DisagreePercent); err != nil {
utils.Logger().Println(err)
}
}
How to get a similar result? As you can see each object inside the array is grouped by value in the category column:
[
{
category: "Policy",
questions: ["Do you support the President's policy?", "Do you support Democrats?"],
series: [
{
name: "Agree, %",
data: [50, 32]
},
{
name: "Disagree, %",
data: [50, 68]
},
]
},
{
category: "Cinema",
questions: ["Do you support the Lannisters?", "Do you support Spielberg's work?"],
series: [
{
name: "Agree, %",
data: [45, 60]
},
{
name: "Disagree, %",
data: [55, 40]
},
]
},
]

Answer 1

Well, I can't say that it's elegant way, but finally I solve my task:
// Create struct called "Series".
type Series struct {
Name string `json:"name"`
Data []float64 `json:"data"`
}
// Create struct called "Specification".
type Specification struct {
Category string `json:"category"`
Questions []string `json:"questions"`
Series []Series `json:"series"`
}
// Initialize an array of struct.
var specifications []Specification
// Initialize several variables.
var catogoryName string
var arrayQuestionText []string
var arrayAgreePercent []float64
var arrayDisagreePercent []float64
for rows.Next() {
// Check the change in the name of the category.
if entry.Category == catogoryName {
// Add new elements to arrays.
arrayQuestionText = append(arrayQuestionText, entry.QuestionText)
arrayDisagreePercent = append(arrayDisagreePercent, entry.DisagreePercent)
arrayAgreePercent = append(arrayAgreePercent, entry.AgreePercent)
} else {
if len(catogoryName) > 0 {
// Fill the struct with data.
specification := Specification{
Category: catogoryName,
Questions: arrayQuestionText,
Series: []Series{
{
Name: "Agree, %",
Data: arrayAgreePercent,
},
{
Name: "Disagree, %",
Data: arrayDisagreePercent,
},
},
}
// Add new struct to array.
specifications = append(specifications, specification)
}
}
// Update data in arrays.
catogoryName = entry.Category
arrayQuestionText = nil
arrayQuestionText = append(arrayQuestionText, entry.QuestionText)
arrayDisagreePercent = nil
arrayDisagreePercent = append(arrayDisagreePercent, entry.DisagreePercent)
arrayAgreePercent = nil
arrayAgreePercent = append(arrayAgreePercent, entry.AgreePercent)
}