diff --git a/apps/api/src/db/schema.ts b/apps/api/src/db/schema.ts
index 591d808..2528de0 100644
--- a/apps/api/src/db/schema.ts
+++ b/apps/api/src/db/schema.ts
@@ -44,13 +44,13 @@ import type {
   FlowchartStatus,
   HintDiagnosis,
   JudgeStatus,
+  LessonLanguage,
   ProblemDifficulty,
   ProblemLanguage,
   ProblemPermission,
   ProblemSetDifficulty,
   ProblemSetStatus,
   ReactionKey,
-  RunnableLanguage,
   SqlConfig,
   SqlDisplay,
   TagCategory,
@@ -1497,10 +1497,10 @@ export const classLesson = pgTable(
     day: text().notNull(),
     problemIds: jsonb("problem_ids").notNull().$type<number[]>(),
     /**
-     * 这份作业用什么语言做（Python / C / C++），老师布置时选。可空：加这一列之前布置的
-     * 没有它。写入侧在 PUT /classroom/lesson 按 runnableLanguageSchema 校验过
+     * 这份作业用什么语言做（Python / C / C++ / SQL），老师布置时选。可空：加这一列之前布置的
+     * 没有它。写入侧在 PUT /classroom/lesson 按 lessonLanguageSchema 校验过
      */
-    language: text().$type<RunnableLanguage>(),
+    language: text().$type<LessonLanguage>(),
     createdBy: integer("created_by").notNull(),
     updatedAt: timestamp("updated_at", {
       withTimezone: true,
diff --git a/apps/api/src/routes/classroom.ts b/apps/api/src/routes/classroom.ts
index 2232d97..a7bceff 100644
--- a/apps/api/src/routes/classroom.ts
+++ b/apps/api/src/routes/classroom.ts
@@ -12,7 +12,7 @@ import {
   type ClassRankItem,
   type ClassUserRank,
   type LastVisit,
-  type RunnableLanguage,
+  type LessonLanguage,
   FLOWCHART_PASS_GRADES,
 } from "@oj2/contract"
 import {
@@ -221,12 +221,21 @@ function classMemberIds(className: string) {
  * 有的题一节课全班都在画流程图、代码提交个位数，只数代码的话这节课在统计里等于没上。
  * 两边都按 `user_id in (...)` + `create_time >=` 走各自的 (user_id, create_time) 索引。
  */
+/**
+ * 老师布置时选了语言：代码只数这个语言交的。SQL 题例外 —— 它只收 SQL，按 C 去数的话，
+ * C 的作业里夹一道 SQL 题，学生怎么交都算不了做完。非 SQL 题交不进 SQL（提交接口按题目的
+ * 语言拦），所以一律放行 SQL 不会把别的题算宽
+ */
+function lessonLanguageFilter(language: LessonLanguage | null | undefined) {
+  return language ? inArray(schema.submission.language, [language, "SQL"]) : undefined
+}
+
 function activityRows(options: {
   since: string
   users?: number[] | ReturnType<typeof classMemberIds>
   problemIds?: number[]
-  /** 老师布置时选了语言：代码只数这个语言交的，流程图不受影响 */
-  language?: RunnableLanguage | null
+  /** 老师布置时选了语言：代码只数这个语言交的（见 lessonLanguageFilter），流程图不受影响 */
+  language?: LessonLanguage | null
 }) {
   const { since, users, problemIds, language } = options
   const code = db
@@ -243,7 +252,7 @@ function activityRows(options: {
         gte(schema.submission.createTime, since),
         users ? inArray(schema.submission.userId, users) : undefined,
         problemIds ? inArray(schema.submission.problemId, problemIds) : undefined,
-        language ? eq(schema.submission.language, language) : undefined,
+        lessonLanguageFilter(language),
       ),
     )
   const flowchart = db
@@ -272,7 +281,7 @@ function activityRows(options: {
 async function classDayGroups(
   className: string,
   since: string,
-  options: { minUsers?: number; problemIds?: number[]; language?: RunnableLanguage | null } = {},
+  options: { minUsers?: number; problemIds?: number[]; language?: LessonLanguage | null } = {},
 ): Promise<ClassDayGroup[]> {
   const activity = activityRows({
     since,
@@ -297,12 +306,14 @@ async function classDayGroups(
 
 /** 按 id 取题，只留学生看得见的（题库里、visible），被藏起来的点进去也是 404 */
 async function visibleProblems(ids: number[]) {
-  if (!ids.length) return new Map<number, { id: number; displayId: string; title: string }>()
+  if (!ids.length)
+    return new Map<number, { id: number; displayId: string; title: string; isSql: boolean }>()
   const rows = await db
     .select({
       id: schema.problem.id,
       displayId: schema.problem.displayId,
       title: schema.problem.title,
+      isSql: sql<boolean>`${schema.problem.languages} @> '["SQL"]'::jsonb`,
     })
     .from(schema.problem)
     .where(
@@ -533,7 +544,7 @@ classroomRoutes.get("/me/class-activity", requireAuth, async (c) => {
               inArray(schema.submission.problemId, ids),
               isNull(schema.submission.contestId),
               // 布置的是 C：以前用 Python 做对过不算这份作业做完
-              lesson.language ? eq(schema.submission.language, lesson.language) : undefined,
+              lessonLanguageFilter(lesson.language),
             ),
           )
           .groupBy(schema.submission.problemId)
@@ -706,7 +717,7 @@ classroomRoutes.get("/classroom/board", requireTeacher, async (c) => {
               isNull(schema.submission.contestId),
               inArray(schema.submission.userId, userIds),
               inArray(schema.submission.problemId, ids),
-              lesson.language ? eq(schema.submission.language, lesson.language) : undefined,
+              lessonLanguageFilter(lesson.language),
             ),
           )
           .groupBy(schema.submission.userId, schema.submission.problemId)
@@ -807,6 +818,7 @@ classroomRoutes.get("/classroom/board", requireTeacher, async (c) => {
       problemId: problem.id,
       problemDisplayId: problem.displayId,
       title: problem.title,
+      isSql: problem.isSql,
     })),
     students: roster.map(
       (student) =>
@@ -852,10 +864,12 @@ classroomRoutes.get("/classroom/lesson", requireTeacher, async (c) => {
     } satisfies ClassLesson)
   // 和看板一样只回看今天：「这节课」不该冒出昨天的题
   const lesson = await classLessonProblems(className, 1)
+  // C / Python 的作业夹了 SQL 题就不筛语言（见契约 classLessonSchema.language）
+  const mixed = lesson.problems.some((problem) => problem.isSql !== (lesson.language === "SQL"))
   return success(c, {
     className,
     source: lesson.source,
-    language: lesson.language,
+    language: mixed ? null : lesson.language,
     problems: lesson.problems.map((problem) => ({
       problemDisplayId: problem.displayId,
       title: problem.title,
@@ -911,10 +925,11 @@ classroomRoutes.put("/classroom/lesson", requireTeacher, async (c) => {
     return failure(c, 400, "problem-not-found", `这些题号不存在或没有公开：${missing.join("、")}`)
   }
 
-  // 选了语言就得每道都能用它交，不然学生点开才发现交不了（提交接口会拒：language-not-allowed）
+  // 选了语言就得每道都能用它交，不然学生点开才发现交不了（提交接口会拒：language-not-allowed）。
+  // SQL 题除外：它只收 SQL，C 的作业里夹一道也不会让人选错语言，计数那边也放行了 SQL
   if (language) {
     const unsupported = found
-      .filter((row) => !row.languages.includes(language))
+      .filter((row) => !row.languages.includes(language) && !row.languages.includes("SQL"))
       .map((row) => row.displayId)
     if (unsupported.length) {
       return failure(
diff --git a/apps/web/src/oj/api.ts b/apps/web/src/oj/api.ts
index 4d60d36..cc8be3b 100644
--- a/apps/web/src/oj/api.ts
+++ b/apps/web/src/oj/api.ts
@@ -42,7 +42,7 @@ import {
   type FlowchartStatistics,
   type SubmissionStatistics,
   type SubmissionLessons,
-  type RunnableLanguage,
+  type LessonLanguage,
   type SubmissionStatisticsGrid,
   type TodaySubmissionStatistics,
 } from "@oj2/contract"
@@ -261,7 +261,7 @@ export function getClassLesson(className?: string) {
 export function setClassLesson(
   className: string,
   problemDisplayIds: string[],
-  language: RunnableLanguage | null,
+  language: LessonLanguage | null,
 ) {
   return api.put<null>("classroom/lesson", { className, problemDisplayIds, language })
 }
diff --git a/apps/web/src/oj/classroom/board.vue b/apps/web/src/oj/classroom/board.vue
index 46b9632..c6f249b 100644
--- a/apps/web/src/oj/classroom/board.vue
+++ b/apps/web/src/oj/classroom/board.vue
@@ -3,11 +3,11 @@ import { getClassBoard, setClassLesson } from "oj/api"
 import { useLeaveStudents } from "shared/composables/leaveStudents"
 import { useCollabStore } from "shared/store/collab"
 import { useConfigStore } from "shared/store/config"
-import type { RunnableLanguage } from "@oj2/contract"
+import type { LessonLanguage } from "@oj2/contract"
 import { errorMessage } from "utils/api"
 import { LANGUAGE_SHOW_VALUE } from "utils/constants"
 import { parseTime } from "utils/functions"
-import type { ClassBoard, ClassBoardCell, ClassBoardStudent } from "utils/types"
+import type { ClassBoard, ClassBoardCell, ClassBoardProblem, ClassBoardStudent } from "utils/types"
 
 /**
  * 课堂看板（老师）：这个班、今天、这节课的几道题 × 全班学生。
@@ -40,8 +40,8 @@ const lessonInput = ref("")
  * 这份作业用什么语言做，跟着这一次布置走（用户定的：不是给班级定死的设置）。默认是这个班
  * 上一次布置时选的；选了之后看板和学生那边的「做完」都只认这个语言交对的
  */
-const lessonLanguage = ref<RunnableLanguage>("Python")
-const LESSON_LANGUAGES: RunnableLanguage[] = ["Python", "C", "C++"]
+const lessonLanguage = ref<LessonLanguage>("Python")
+const LESSON_LANGUAGES: LessonLanguage[] = ["Python", "C", "C++", "SQL"]
 const languageOptions = LESSON_LANGUAGES.map((value) => ({
   label: LANGUAGE_SHOW_VALUE[value],
   value,
@@ -291,9 +291,11 @@ const router = useRouter()
  */
 function submissionsHref(
   student: ClassBoardStudent,
-  problemDisplayId: string | undefined,
+  problem: ClassBoardProblem | undefined,
   flowchart: boolean,
 ) {
+  // SQL 题不受布置的语言限制，格子数的是 SQL 交的
+  const language = problem?.isSql ? "SQL" : board.value?.language
   return router.resolve({
     name: "submissions",
     query: {
@@ -301,12 +303,8 @@ function submissionsHref(
       exactUsername: "1",
       today: "1",
       // 布置时选了语言的，代码那边只看这个语言交的（和格子里数的一致）
-      ...(flowchart
-        ? { language: "Flowchart" }
-        : board.value?.language
-          ? { language: board.value.language }
-          : {}),
-      ...(problemDisplayId ? { problem: problemDisplayId } : {}),
+      ...(flowchart ? { language: "Flowchart" } : language ? { language } : {}),
+      ...(problem ? { problem: problem.problemDisplayId } : {}),
     },
   }).href
 }
@@ -388,7 +386,10 @@ function submissionsHref(
         <n-text depth="3" class="meta">
           <template v-if="board.source === 'teacher'">
             学生首页的「班里在做」显示的就是这几道<template v-if="board.language"
-              >，用 {{ LANGUAGE_SHOW_VALUE[board.language] }} 交对才算做完</template
+              >，用 {{ LANGUAGE_SHOW_VALUE[board.language] }} 交对才算做完<template
+                v-if="board.language !== 'SQL' && board.problems.some((p) => p.isSql)"
+                >（SQL 题交对 SQL 就算）</template
+              ></template
             >。清空再点布置就改回自动推断。
           </template>
           <template v-else-if="board.source === 'inferred'">
@@ -515,13 +516,7 @@ function submissionsHref(
                       <a
                         v-if="cell.attempts"
                         class="cell-link"
-                        :href="
-                          submissionsHref(
-                            student,
-                            board.problems[i]!.problemDisplayId,
-                            !cell.codeAttempts,
-                          )
-                        "
+                        :href="submissionsHref(student, board.problems[i], !cell.codeAttempts)"
                         target="_blank"
                         :title="
                           cell.codeAttempts
diff --git a/apps/web/src/utils/types.ts b/apps/web/src/utils/types.ts
index cbd1b2d..444ec1a 100644
--- a/apps/web/src/utils/types.ts
+++ b/apps/web/src/utils/types.ts
@@ -300,7 +300,13 @@ export type { ClassComparison, ClassRankItem, ClassUserRank } from "@oj2/contrac
 export type { ClassActivity, ClassActivityProblem, LastVisit } from "@oj2/contract"
 
 /** 课堂看板：一个班今天这节课的题 × 全班学生 */
-export type { ClassBoard, ClassBoardStudent, ClassBoardCell, ClassLesson } from "@oj2/contract"
+export type {
+  ClassBoard,
+  ClassBoardProblem,
+  ClassBoardStudent,
+  ClassBoardCell,
+  ClassLesson,
+} from "@oj2/contract"
 
 /** 知识点地图：每个知识点做对几道、在第几档，只给自己看 */
 export type { KnowledgeLevel, KnowledgeMap } from "@oj2/contract"
diff --git a/packages/contract/src/classroom.ts b/packages/contract/src/classroom.ts
index fd219dd..1e881c1 100644
--- a/packages/contract/src/classroom.ts
+++ b/packages/contract/src/classroom.ts
@@ -1,7 +1,7 @@
 import { z } from "zod"
 
 import { judgeStatusSchema } from "./judge-status"
-import { runnableLanguageSchema } from "./language"
+import { lessonLanguageSchema as lessonLanguageValueSchema } from "./language"
 
 export const classRankItemSchema = z.object({
   className: z.string(),
@@ -85,10 +85,11 @@ export const classActivityProblemSchema = z.object({
 })
 
 /**
- * 老师布置这节课时选的语言（Python / C / C++）。null = 没选：推断出来的课、加这一项之前
- * 布置的课。选了之后这份作业「做完」只认这个语言交对的，学生打开这几道题编辑器默认就是它
+ * 老师布置这节课时选的语言（Python / C / C++ / SQL）。null = 没选：推断出来的课、加这一项之前
+ * 布置的课。选了之后这份作业「做完」只认这个语言交对的（SQL 题例外，交对 SQL 就算），
+ * 学生打开这几道题编辑器默认就是它
  */
-const lessonLanguageSchema = runnableLanguageSchema.nullable()
+const lessonLanguageSchema = lessonLanguageValueSchema.nullable()
 
 export const classActivitySchema = z.object({
   className: z.string().nullable(),
@@ -147,6 +148,8 @@ export const classBoardProblemSchema = z.object({
   problemId: z.number().int(),
   problemDisplayId: z.string(),
   title: z.string(),
+  /** SQL 题不受布置的语言限制：格子数的是 SQL 交的，点进提交列表也按 SQL 筛 */
+  isSql: z.boolean(),
 })
 
 export const classBoardCellSchema = z.object({
@@ -214,7 +217,10 @@ export const classBoardSchema = z.object({
 export const classLessonSchema = z.object({
   className: z.string().nullable(),
   source: z.enum(["teacher", "inferred"]).nullable(),
-  /** 选了语言时，列表那边连语言一起筛 */
+  /**
+   * 选了语言时，列表那边连语言一起筛。C / Python 的作业里夹了 SQL 题就是 null：
+   * 列表只能筛一种语言，按 C 筛会把 SQL 题交的全藏起来，宁可多列一些
+   */
   language: lessonLanguageSchema,
   problems: z.array(z.object({ problemDisplayId: z.string(), title: z.string() })),
 })
diff --git a/packages/contract/src/language.ts b/packages/contract/src/language.ts
index 309545f..2796896 100644
--- a/packages/contract/src/language.ts
+++ b/packages/contract/src/language.ts
@@ -43,7 +43,14 @@ export const problemLanguageSchema = z.enum([...judgeLanguageSchema.options, "SQ
  */
 export const runnableLanguageSchema = judgeLanguageSchema.extract(["C", "C++", "Python"])
 
+/**
+ * 老师布置作业能选的语言：判题机跑得了的三种，加 SQL（数据库课一整节都是 SQL 题）。
+ * SQL 题只收 SQL，所以 C / Python 的作业里夹 SQL 题也行 —— 那几道不受作业语言限制
+ */
+export const lessonLanguageSchema = problemLanguageSchema.extract(["Python", "C", "C++", "SQL"])
+
 export type JudgeLanguage = z.infer<typeof judgeLanguageSchema>
+export type LessonLanguage = z.infer<typeof lessonLanguageSchema>
 export type RunnableLanguage = z.infer<typeof runnableLanguageSchema>
 export type ProblemLanguage = z.infer<typeof problemLanguageSchema>