fix: MySQL parameter binding compatibility with SQLAlchemy

- Convert MySQL '?' placeholders to named parameters (':p1', ':p2', etc.)
  for proper SQLAlchemy parameter binding
- Add MySQL type mapping support for Python type inference
- Fix SQL syntax error when using generated code with MySQL + SQLAlchemy

The generated code was using '?' placeholders in SQL but passing named
parameters as dictionaries, which caused MySQL syntax errors. This fix
ensures the SQL uses named parameters that match the parameter binding.

Fixes parameter binding issues for MySQL users of sqlc-gen-python.

Author: santinalbrowns

internal/gen.go

@@ -193,8 +193,10 @@ func pyInnerType(req *plugin.GenerateRequest, col *plugin.Column) string {
 	switch req.Settings.Engine {
 	case "postgresql":
 		return postgresType(req, col)
+	case "mysql":
+		return mysqlType(req, col)
 	default:
-		log.Println("unsupported engine type")
+		log.Printf("unsupported engine type: %s\n", req.Settings.Engine)
 		return "Any"
 	}
 }
@@ -360,6 +362,14 @@ func sqlalchemySQL(s, engine string) string {
 	if engine == "postgresql" {
 		return postgresPlaceholderRegexp.ReplaceAllString(s, ":p$1")
 	}
+	if engine == "mysql" {
+		// Convert MySQL ? placeholders to named parameters for SQLAlchemy compatibility
+		i := 1
+		for strings.Contains(s, "?") {
+			s = strings.Replace(s, "?", fmt.Sprintf(":p%d", i), 1)
+			i++
+		}
+	}
 	return s
 }
 

internal/mysql_type.go

@@ -0,0 +1,53 @@
+package python
+
+import (
+	"log"
+
+	"github.com/sqlc-dev/plugin-sdk-go/plugin"
+	"github.com/sqlc-dev/plugin-sdk-go/sdk"
+)
+
+func mysqlType(req *plugin.GenerateRequest, col *plugin.Column) string {
+	columnType := sdk.DataType(col.Type)
+
+	switch columnType {
+	case "tinyint", "smallint", "mediumint", "int", "integer", "bigint":
+		return "int"
+	case "float", "double", "real":
+		return "float"
+	case "decimal", "numeric":
+		return "decimal.Decimal"
+	case "bit", "boolean", "bool":
+		return "bool"
+	case "json":
+		return "Any"
+	case "binary", "varbinary", "blob", "tinyblob", "mediumblob", "longblob":
+		return "memoryview"
+	case "date":
+		return "datetime.date"
+	case "time":
+		return "datetime.time"
+	case "datetime", "timestamp":
+		return "datetime.datetime"
+	case "char", "varchar", "text", "tinytext", "mediumtext", "longtext":
+		return "str"
+	case "enum", "set":
+		return "str"
+	default:
+		for _, schema := range req.Catalog.Schemas {
+			if schema.Name == "information_schema" || schema.Name == "mysql" {
+				continue
+			}
+			for _, enum := range schema.Enums {
+				if columnType == enum.Name {
+					if schema.Name == req.Catalog.DefaultSchema {
+						return "models." + modelName(enum.Name, req.Settings)
+					}
+					return "models." + modelName(schema.Name+"_"+enum.Name, req.Settings)
+				}
+			}
+		}
+		log.Printf("unknown MySQL type: %s\n", columnType)
+		return "Any"
+	}
+}