test: add type inference test examples for MySQL

Add comprehensive test cases to validate expression type inference:
- Simple division operations (a1 / 1024)
- CAST with COALESCE combinations
- Explicit CAST operations
- Arithmetic operations (+, -, *, %)
- COALESCE with inferred types

These examples help verify that the type inference system correctly
handles mathematical expressions and nullable columns.

Author: rubensantoniorosa2704

examples/type-inference-test/mysql/query.sql

@@ -0,0 +1,28 @@
+-- name: ListTest :many
+SELECT 
+    (a1 / 1024) a1_float, (a2 / 1024) a2_float, a3
+FROM test;
+
+-- name: ListTest2 :many
+SELECT 
+    COALESCE(CAST(a1 / 1024 AS FLOAT), 0) a1_float, COALESCE(CAST(a2 / 1024 AS FLOAT), 0) a2_float, a3
+FROM test;
+
+-- name: ListTest3 :many
+SELECT 
+    CAST(a1 / 1024 AS FLOAT) a1_float, CAST(a2 / 1024 AS FLOAT) a2_float, a3
+FROM test;
+
+-- name: ListTest4 :many
+SELECT 
+    (a1 + a2) as sum_result,
+    (a1 * a2) as mult_result,
+    (a1 - a2) as sub_result,
+    (a1 % 10) as mod_result
+FROM test;
+
+-- name: ListTest5 :many
+SELECT 
+    COALESCE(a1 / 1024, 0) as with_inference,
+    COALESCE(a2 / 1024, 0) as nullable_inference
+FROM test;

examples/type-inference-test/mysql/schema.sql

@@ -0,0 +1,6 @@
+CREATE TABLE test (
+    id INT PRIMARY KEY AUTO_INCREMENT,
+    a1 INT NOT NULL,
+    a2 INT NULL,
+    a3 FLOAT NOT NULL
+);

examples/type-inference-test/sqlc.yaml

@@ -0,0 +1,13 @@
+version: "2"
+sql:
+  - engine: "mysql"
+    queries: "mysql/query.sql"
+    schema: "mysql/schema.sql"
+    gen:
+      go:
+        package: "mysql"
+        out: "mysql"
+        emit_json_tags: true
+        emit_prepared_queries: false
+        emit_interface: false
+        emit_exact_table_names: false