Update SQLite3_ The columntypescantype method of type (#909)

* sqlite3_type update

The main reason for this change is that the original reflected values are nil. I found that there was no good mapping when dealing with the code here

* Update sqlite3_type.go

Update 'ColumnTypeScanType' method,
Different types of mapping values

* Restore copyright

* Update go.mod

* Update go.mod

sqlite3_type.go

@@ -1,5 +1,4 @@
 // Copyright (C) 2019 Yasuhiro Matsumoto <mattn.jp@gmail.com>.
-//
 // Use of this source code is governed by an MIT-style
 // license that can be found in the LICENSE file.
 
@@ -14,8 +13,9 @@ package sqlite3
 */
 import "C"
 import (
+	"database/sql"
 	"reflect"
-	"time"
+	"strings"
 )
 
 // ColumnTypeDatabaseTypeName implement RowsColumnTypeDatabaseTypeName.
@@ -31,32 +31,78 @@ func (rc *SQLiteRows) ColumnTypeLength(index int) (length int64, ok bool) {
 func (rc *SQLiteRows) ColumnTypePrecisionScale(index int) (precision, scale int64, ok bool) {
 	return 0, 0, false
 }
+*/
 
 // ColumnTypeNullable implement RowsColumnTypeNullable.
 func (rc *SQLiteRows) ColumnTypeNullable(i int) (nullable, ok bool) {
-	return false, false
+	return true, true
 }
-*/
 
 // ColumnTypeScanType implement RowsColumnTypeScanType.
 func (rc *SQLiteRows) ColumnTypeScanType(i int) reflect.Type {
-	switch C.sqlite3_column_type(rc.s.s, C.int(i)) {
-	case C.SQLITE_INTEGER:
-		switch C.GoString(C.sqlite3_column_decltype(rc.s.s, C.int(i))) {
-		case "timestamp", "datetime", "date":
-			return reflect.TypeOf(time.Time{})
-		case "boolean":
-			return reflect.TypeOf(false)
-		}
-		return reflect.TypeOf(int64(0))
-	case C.SQLITE_FLOAT:
-		return reflect.TypeOf(float64(0))
-	case C.SQLITE_BLOB:
-		return reflect.SliceOf(reflect.TypeOf(byte(0)))
-	case C.SQLITE_NULL:
-		return reflect.TypeOf(nil)
-	case C.SQLITE_TEXT:
-		return reflect.TypeOf("")
-	}
-	return reflect.SliceOf(reflect.TypeOf(byte(0)))
+	//ct := C.sqlite3_column_type(rc.s.s, C.int(i))  // Always returns 5
+	return scanType(C.GoString(C.sqlite3_column_decltype(rc.s.s, C.int(i))))
+}
+
+const (
+	SQLITE_INTEGER = iota
+	SQLITE_TEXT
+	SQLITE_BLOB
+	SQLITE_REAL
+	SQLITE_NUMERIC
+	SQLITE_TIME
+	SQLITE_BOOL
+	SQLITE_NULL
+)
+
+func scanType(cdt string) reflect.Type {
+	t := strings.ToUpper(cdt)
+	i := databaseTypeConvSqlite(t)
+	switch i {
+	case SQLITE_INTEGER:
+		return reflect.TypeOf(sql.NullInt64{})
+	case SQLITE_TEXT:
+		return reflect.TypeOf(sql.NullString{})
+	case SQLITE_BLOB:
+		return reflect.TypeOf(sql.RawBytes{})
+	case SQLITE_REAL:
+		return reflect.TypeOf(sql.NullFloat64{})
+	case SQLITE_NUMERIC:
+		return reflect.TypeOf(sql.NullFloat64{})
+	case SQLITE_BOOL:
+		return reflect.TypeOf(sql.NullBool{})
+	case SQLITE_TIME:
+		return reflect.TypeOf(sql.NullTime{})
+	}
+	return reflect.TypeOf(new(interface{}))
+}
+
+func databaseTypeConvSqlite(t string) int {
+	if strings.Contains(t, "INT") {
+		return SQLITE_INTEGER
+	}
+	if t == "CLOB" || t == "TEXT" ||
+		strings.Contains(t, "CHAR") {
+		return SQLITE_TEXT
+	}
+	if t == "BLOB" {
+		return SQLITE_BLOB
+	}
+	if t == "REAL" || t == "FLOAT" ||
+		strings.Contains(t, "DOUBLE") {
+		return SQLITE_REAL
+	}
+	if t == "DATE" || t == "DATETIME" ||
+		t == "TIMESTAMP" {
+		return SQLITE_TIME
+	}
+	if t == "NUMERIC" ||
+		strings.Contains(t, "DECIMAL") {
+		return SQLITE_NUMERIC
+	}
+	if t == "BOOLEAN" {
+		return SQLITE_BOOL
+	}
+
+	return SQLITE_NULL
 }