Support MSSQL placeholders (#44)

GUIDE.md

@@ -2,7 +2,7 @@
 
 ## Safety & Sanitization
 
-Query arguments should be passed via `%$` or `%?`, this way they won't appear in the query string but instead will be appended to the arguments slice (2nd return value of the `Builder.Build()` method), thus preventing potential SQL injections.
+Query arguments should be passed via `%$`, `%?`, or `%@`, this way they won't appear in the query string but instead will be appended to the arguments slice (2nd return value of the `Builder.Build()` method), thus preventing potential SQL injections.
 
 Examples in [example_test.go](example_test.go) explicitly show that query arguments are not a part of the `query` string but returned separately as the `args` slice.
 
@@ -63,16 +63,17 @@ Please note that unlike `fmt`, `builq` does not support width and explicit argum
 
 ## Argument placeholder
 
-`builq` supports only 2 popular formats:
+`builq` supports 3 formats:
 
 * PostgreSQL via `%$` (`$1, $2, $3..`)
 * MySQL/SQLite via `%?` (`?, ?, ?..`)
+* MSSQL via `%@` (`@p1, @p2, @p3..`)
 
 This should cover almost all available databases, if not - feel free to make an issue.
 
 ## Slice/batch modifiers
 
-Both `%$` and `%?` formats can be extended with `+` or `#`:
+All formats can be extended with `+` or `#`:
 
 * `%+$` will expand slice argument as `$1, $2, ... $(len(arg)-1)`
 * `%#?` will expand slice of slices argument as `(?, ?), (?, ?), ... (?, ?)`
@@ -101,4 +102,4 @@ BenchmarkBuildManyArgs-10    	   85747	     14027 ns/op	    1056 B/op	      24 a
 BenchmarkBuildCached
 BenchmarkBuildCached-10      	1000000000	         0.6213 ns/op	       0 B/op	       0 allocs/op
 PASS
-```
+```

example_test.go

@@ -379,6 +379,31 @@ func Example_sliceMySQL() {
 	// [42 true str]
 }
 
+func Example_sliceMSSQL() {
+	params := []any{42, true, "str"}
+
+	var b builq.Builder
+	b.Addf("INSERT INTO table (id, flag, name)")
+	b.Addf("VALUES (%+@);", params)
+
+	query, args, err := b.Build()
+	if err != nil {
+		panic(err)
+	}
+
+	fmt.Println("query:")
+	fmt.Println(query)
+	fmt.Println("args:")
+	fmt.Println(args)
+
+	// Output:
+	// query:
+	// INSERT INTO table (id, flag, name)
+	// VALUES (@p1, @p2, @p3);
+	// args:
+	// [42 true str]
+}
+
 func Example_insertReturn() {
 	cols := builq.Columns{"id", "is_active", "name"}
 	params := []any{true, "str"}
@@ -463,6 +488,34 @@ func Example_batchMySQL() {
 	// [42 true str 69 true noice]
 }
 
+func Example_batchMSSQL() {
+	params := [][]any{
+		{42, true, "str"},
+		{69, true, "noice"},
+	}
+
+	var b builq.Builder
+	b.Addf("INSERT INTO table (id, flag, name)")
+	b.Addf("VALUES %#@;", params)
+
+	query, args, err := b.Build()
+	if err != nil {
+		panic(err)
+	}
+
+	fmt.Println("query:")
+	fmt.Println(query)
+	fmt.Println("args:")
+	fmt.Println(args)
+
+	// Output:
+	// query:
+	// INSERT INTO table (id, flag, name)
+	// VALUES (@p1, @p2, @p3), (@p4, @p5, @p6);
+	// args:
+	// [42 true str 69 true noice]
+}
+
 func Example_sliceInBatch() {
 	params := [][]any{
 		{42, []any{1, 2, 3}},

write.go

@@ -30,7 +30,7 @@ func (b *Builder) write(sb *strings.Builder, resArgs *[]any, s string, args ...a
 		}
 
 		switch verb := s[0]; verb {
-		case '$', '?', 's', 'd':
+		case '$', '?', '@', 's', 'd':
 			if argID >= len(args) {
 				return fmt.Errorf("%w: have %d args, want %d", errTooFewArguments, len(args), argID+1)
 			}
@@ -49,7 +49,7 @@ func (b *Builder) write(sb *strings.Builder, resArgs *[]any, s string, args ...a
 			}
 
 			switch verb := s[0]; verb {
-			case '$', '?':
+			case '$', '?', '@':
 				if argID >= len(args) {
 					return fmt.Errorf("%w: have %d args, want %d", errTooFewArguments, len(args), argID+1)
 				}
@@ -136,6 +136,11 @@ func (b *Builder) writeArg(sb *strings.Builder, resArgs *[]any, verb byte, arg a
 	case '?':
 		sb.WriteByte('?')
 		*resArgs = append(*resArgs, arg)
+	case '@':
+		b.counter++
+		sb.WriteString("@p")
+		sb.WriteString(strconv.Itoa(b.counter))
+		*resArgs = append(*resArgs, arg)
 	case 's':
 		isSimple = true
 		switch arg := arg.(type) {