fix(sql): make fee migration MySQL-compatible

firstleg/src/test/java/com/baiyue/firstleg/repository/FeeItemMigrationSqlContractTest.java

@@ -0,0 +1,36 @@
+package com.baiyue.firstleg.repository;
+
+import org.junit.jupiter.api.Test;
+
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class FeeItemMigrationSqlContractTest {
+    @Test
+    void temporarySeedTableIsNotReopenedWithinOneMysqlStatement() throws Exception {
+        assertMysqlCompatible(resolve("deploy/sql/头程数据库统一增量-MySQL8.sql"));
+        assertMysqlCompatible(resolve(
+            "firstleg/src/main/resources/db/phase2-published-freight-detail-migration.sql"));
+    }
+
+    private static void assertMysqlCompatible(Path path) throws Exception {
+        String sql = Files.readString(path, StandardCharsets.UTF_8);
+        assertThat(sql)
+            .contains("LEFT JOIN tmp_fee_item_seed matched_seed")
+            .contains("matched_seed.fee_code = NULLIF(TRIM(f.fee_code), '')")
+            .contains("matched_seed.trade_scope = f.trade_scope")
+            .doesNotContain("LEFT JOIN tmp_fee_item_seed by_code")
+            .doesNotContain("LEFT JOIN tmp_fee_item_seed by_semantic")
+            .doesNotContain("OR (SELECT COUNT(*) FROM tmp_fee_item_seed")
+            .doesNotContain("OR EXISTS (SELECT trade_scope, fee_type_name FROM tmp_fee_item_seed");
+    }
+
+    private static Path resolve(String value) {
+        Path direct = Path.of(value);
+        if (Files.exists(direct)) return direct;
+        return Path.of("..", value).normalize();
+    }
+}