Cleanup parser statements, add delete and insert statement, add TASKS.md for tracking tasks

sql/lexer.go

@@ -29,6 +29,11 @@ const (
 	CREATE
 	TABLE
 
+	INSERT
+	INTO
+	VALUES
+	RETURNING
+
 	SELECT
 	FROM
 	WHERE
@@ -37,6 +42,8 @@ const (
 	ORDER
 	TOP
 
+	DELETE
+
 	PRIMARY
 	FOREIGN
 	REFERENCES
@@ -80,6 +87,11 @@ var keywords map[string]Token = map[string]Token{
 	"AUTOINCREMENT": AUTOINCREMENT,
 	"CONSTRAINT":    CONSTRAINT,
 	"NUMERIC":       NUMERIC,
+	"INSERT":        INSERT,
+	"INTO":          INTO,
+	"VALUES":        VALUES,
+	"RETURNING":     RETURNING,
+	"DELETE":        DELETE,
 }
 
 type Position struct {