Added ability to open existing SQLite DBs

Author: dhamith93

README.md

@@ -1,19 +1,26 @@
 # csv-sql
-Command-line tool to load csv and xlsx files and run sql commands 
+Command-line tool to load csv and excel (xlsx) files and run sql commands 
 
 [![Go](https://github.com/dhamith93/csv-sql/actions/workflows/go.yml/badge.svg)](https://github.com/dhamith93/csv-sql/actions/workflows/go.yml)
 
 ## Usage
 
 csv-sql supports loading and saving results as CSV and XLSX files with data processing with SQLite compatible sql commands.
 
+Also, this can be used to open existing SQLite DBs and extract data as CSV.
+
 ### Loading a file
 ```
 LOAD /path/to/file table_name
 ```
 You can set up headers if the first row is not a header.
 For XLSX files, when loading, this will ask to select the sheet of the file to load.
 
+### Opening a existing SQLite DB
+```
+DB /path/to/db
+```
+
 ### Creating a new table with a select query
 ```sql
 CREATE TABLE emp_user AS SELECT emp.emp_id, emp.name, user.user_name, user.role FROM emp INNER JOIN user ON emp.user_id = user.id

helpers/completer.go

@@ -6,6 +6,7 @@ func Completer(d prompt.Document) []prompt.Suggest {
 	s := []prompt.Suggest{
 		{Text: "LOAD", Description: "LOAD /path/to/file table_name"},
 		{Text: "SAVE", Description: "SAVE table_name /path/to/file"},
+		{Text: "DB", Description: "DB /path/to/sqlite/db"},
 		{Text: "SHOW TABLES", Description: ""},
 		{Text: "EXIT", Description: ""},
 		{Text: "SELECT", Description: ""},

helpers/data.go

@@ -3,12 +3,43 @@ package helpers
 import (
 	"csv-sql/entity"
 	"database/sql"
+	"errors"
 	"fmt"
+	"log"
+	"os"
 	"strings"
 
 	_ "github.com/mattn/go-sqlite3"
 )
 
+func OpenDB(db *sql.DB, dbName string) (*sql.DB, error) {
+	mimetype, err := GetMimeType(dbName)
+	if err != nil {
+		return db, err
+	}
+
+	if mimetype != "application/x-sqlite3" {
+		return db, errors.New("file is not a sqlite db")
+	}
+
+	db.Close()
+	db, err = sql.Open("sqlite3", dbName)
+	if err != nil {
+		return db, err
+	}
+	return db, nil
+}
+
+func CreateDB(dbName string) *sql.DB {
+	file, err := os.Create(dbName)
+	if err != nil {
+		log.Fatal(err.Error())
+	}
+	file.Close()
+	db, _ := sql.Open("sqlite3", dbName)
+	return db
+}
+
 func PopulateTables(db *sql.DB, file *entity.File) {
 	header := ""
 	for i := 0; i < len(file.Headers); i++ {

helpers/display.go

@@ -2,7 +2,7 @@ package helpers
 
 import (
 	"csv-sql/entity"
-	"fmt"
+	"database/sql"
 	"os"
 	"strings"
 
@@ -19,9 +19,26 @@ func PrintTable(resultTable entity.Table) {
 	table.Render()
 }
 
-func PrintFiles(files []entity.File) {
-	fmt.Println("---")
-	for _, file := range files {
-		fmt.Printf("Table: %v\nHeaders: %v\nPath: %v\n---\n", file.Table, strings.Join(file.Headers, ", "), file.Path)
+func ShowTables(db *sql.DB) {
+	tableNamesQuery := "SELECT name FROM sqlite_master"
+	tableNames := GetData(db, tableNamesQuery)
+	result := make([][]string, 0)
+	resultTable := entity.Table{
+		Headers: []string{"table", "columns"},
 	}
+
+	for _, table := range tableNames.Data {
+		columnNamesQuery := "SELECT name FROM pragma_table_info('" + table[0] + "')"
+		columnNames := GetData(db, columnNamesQuery)
+		var columns []string
+
+		for _, v1 := range columnNames.Data {
+			s := strings.Join(v1, ", ")
+			columns = append(columns, s)
+		}
+		result = append(result, []string{table[0], strings.Join(columns, ", ")})
+	}
+
+	resultTable.Data = result
+	PrintTable(resultTable)
 }

helpers/file.go

@@ -71,3 +71,8 @@ func WriteToCSV(path string, result entity.Table) {
 	csvWriter.Flush()
 	csvFile.Close()
 }
+
+func IsFile(path string) bool {
+	_, err := os.Open(path)
+	return err == nil
+}

main.go

@@ -5,7 +5,6 @@ import (
 	"csv-sql/helpers"
 	"database/sql"
 	"fmt"
-	"log"
 	"os"
 	"os/exec"
 	"strconv"
@@ -21,13 +20,18 @@ func main() {
 	files := make([]entity.File, 0)
 	tableCount := 0
 	dbName := "/tmp/csvql_db_" + helpers.RandSeq(10) + ".db"
-	db := createDB(dbName)
+	db := helpers.CreateDB(dbName)
 	defer db.Close()
 
 	for {
 		response := strings.TrimSpace(prompt.Input("cmd > ", helpers.Completer))
 		responseArr := strings.Fields(response)
 		if len(responseArr) > 0 {
+			if response == "SHOW TABLES" {
+				helpers.ShowTables(db)
+				continue
+			}
+
 			cmd := strings.ToUpper(responseArr[0])
 
 			if cmd == "LOAD" {
@@ -39,13 +43,13 @@ func main() {
 				break
 			}
 
-			if cmd == "SELECT" {
-				helpers.PrintTable(helpers.GetData(db, response))
+			if cmd == "DB" {
+				db = openDB(responseArr, db, dbName)
 				continue
 			}
 
-			if cmd == "SHOW" && response == "SHOW TABLES" {
-				helpers.PrintFiles(files)
+			if cmd == "SELECT" {
+				helpers.PrintTable(helpers.GetData(db, response))
 				continue
 			}
 
@@ -66,6 +70,25 @@ func main() {
 	os.Remove(dbName)
 }
 
+func openDB(responseArr []string, db *sql.DB, dbName string) *sql.DB {
+	if len(responseArr) > 1 {
+		if helpers.IsFile(responseArr[1]) {
+			var err error
+			db, err = helpers.OpenDB(db, responseArr[1])
+
+			if err != nil {
+				fmt.Printf("Error opening DB : %v\n", err.Error())
+				fmt.Println("Falling back to default DB")
+				db, _ = helpers.OpenDB(db, dbName)
+			}
+
+		}
+	} else {
+		fmt.Println("Not a valid file to open as a DB")
+	}
+	return db
+}
+
 func loadFile(responseArr []string, files []entity.File, db *sql.DB, tableCount int) []entity.File {
 	if len(responseArr) == 3 {
 		path := responseArr[1]
@@ -128,7 +151,7 @@ func loadFile(responseArr []string, files []entity.File, db *sql.DB, tableCount
 					content = content[1:]
 				} else {
 					for {
-						fmt.Println("Enter " + strconv.Itoa(len(content[0])) + " headers seperated by commas")
+						fmt.Println("Enter " + strconv.Itoa(len(content[0])) + " headers separated by commas")
 						headers = strings.Split(strings.TrimSpace(prompt.Input("> ", helpers.Completer)), ",")
 						if len(content[0]) == len(headers) {
 							break
@@ -179,16 +202,6 @@ func saveFile(responseArr []string, db *sql.DB, files []entity.File) {
 	}
 }
 
-func createDB(dbName string) *sql.DB {
-	file, err := os.Create(dbName)
-	if err != nil {
-		log.Fatal(err.Error())
-	}
-	file.Close()
-	db, _ := sql.Open("sqlite3", dbName)
-	return db
-}
-
 func validFileType(mimeType string) bool {
 	return mimeType == "text/csv" || mimeType == "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"
 }