diff --git "a/data/1.MySQL\345\210\235\351\230\266/4.\346\225\260\346\215\256\347\261\273\345\236\213/1.\346\225\260\345\200\274\347\261\273\345\236\213/config.json" "b/data/1.MySQL\345\210\235\351\230\266/4.\346\225\260\346\215\256\347\261\273\345\236\213/1.\346\225\260\345\200\274\347\261\273\345\236\213/config.json"
index e3097dce2a72bf8e4da768ca27014664b6582598..aaaab29a1744aeba596872568279d373720ba8cb 100644
--- "a/data/1.MySQL\345\210\235\351\230\266/4.\346\225\260\346\215\256\347\261\273\345\236\213/1.\346\225\260\345\200\274\347\261\273\345\236\213/config.json"
+++ "b/data/1.MySQL\345\210\235\351\230\266/4.\346\225\260\346\215\256\347\261\273\345\236\213/1.\346\225\260\345\200\274\347\261\273\345\236\213/config.json"
@@ -3,7 +3,7 @@
   "keywords": [],
   "children": [],
   "export": [
-    "number.json"
+    "numbers.json"
   ],
   "keywords_must": [],
   "keywords_forbid": [],
diff --git "a/data/1.MySQL\345\210\235\351\230\266/4.\346\225\260\346\215\256\347\261\273\345\236\213/1.\346\225\260\345\200\274\347\261\273\345\236\213/number.json" "b/data/1.MySQL\345\210\235\351\230\266/4.\346\225\260\346\215\256\347\261\273\345\236\213/1.\346\225\260\345\200\274\347\261\273\345\236\213/number.json"
deleted file mode 100644
index a9e2d19b4e857af527b25b0b3b556e6371774fc3..0000000000000000000000000000000000000000
--- "a/data/1.MySQL\345\210\235\351\230\266/4.\346\225\260\346\215\256\347\261\273\345\236\213/1.\346\225\260\345\200\274\347\261\273\345\236\213/number.json"
+++ /dev/null
@@ -1,7 +0,0 @@
-{
-  "type": "code_options",
-  "author": "ccat",
-  "source": "number.md",
-  "notebook_enable": false,
-  "exercise_id": "39244600680e40848e6ab8af71f22cf1"
-}
\ No newline at end of file
diff --git "a/data/1.MySQL\345\210\235\351\230\266/4.\346\225\260\346\215\256\347\261\273\345\236\213/1.\346\225\260\345\200\274\347\261\273\345\236\213/numbers.json" "b/data/1.MySQL\345\210\235\351\230\266/4.\346\225\260\346\215\256\347\261\273\345\236\213/1.\346\225\260\345\200\274\347\261\273\345\236\213/numbers.json"
new file mode 100644
index 0000000000000000000000000000000000000000..4234c280bb3c6bb75a85323185b11c8f651a6938
--- /dev/null
+++ "b/data/1.MySQL\345\210\235\351\230\266/4.\346\225\260\346\215\256\347\261\273\345\236\213/1.\346\225\260\345\200\274\347\261\273\345\236\213/numbers.json"
@@ -0,0 +1,7 @@
+{
+  "type": "code_options",
+  "author": "Mars",
+  "source": "numbers.md",
+  "notebook_enable": false,
+  "exercise_id": "0093549d885b4eec8f556fc86cc60431"
+}
\ No newline at end of file
diff --git "a/data/1.MySQL\345\210\235\351\230\266/4.\346\225\260\346\215\256\347\261\273\345\236\213/2.\346\227\245\346\234\237\345\222\214\346\227\266\351\227\264\347\261\273\345\236\213/config.json" "b/data/1.MySQL\345\210\235\351\230\266/4.\346\225\260\346\215\256\347\261\273\345\236\213/2.\346\227\245\346\234\237\345\222\214\346\227\266\351\227\264\347\261\273\345\236\213/config.json"
index 93b423ee0e18decee539c0ecf687d1217d22b433..bb8b705dfbd6a842d4d4fd9d0f996c19c64f959a 100644
--- "a/data/1.MySQL\345\210\235\351\230\266/4.\346\225\260\346\215\256\347\261\273\345\236\213/2.\346\227\245\346\234\237\345\222\214\346\227\266\351\227\264\347\261\273\345\236\213/config.json"
+++ "b/data/1.MySQL\345\210\235\351\230\266/4.\346\225\260\346\215\256\347\261\273\345\236\213/2.\346\227\245\346\234\237\345\222\214\346\227\266\351\227\264\347\261\273\345\236\213/config.json"
@@ -2,7 +2,9 @@
   "node_id": "mysql-7256fe88bcf241d486c9e2e254ef66d9",
   "keywords": [],
   "children": [],
-  "export": [],
+  "export": [
+    "datetime.json"
+  ],
   "keywords_must": [],
   "keywords_forbid": [],
   "group": 0
diff --git "a/data/1.MySQL\345\210\235\351\230\266/4.\346\225\260\346\215\256\347\261\273\345\236\213/2.\346\227\245\346\234\237\345\222\214\346\227\266\351\227\264\347\261\273\345\236\213/datetime.json" "b/data/1.MySQL\345\210\235\351\230\266/4.\346\225\260\346\215\256\347\261\273\345\236\213/2.\346\227\245\346\234\237\345\222\214\346\227\266\351\227\264\347\261\273\345\236\213/datetime.json"
new file mode 100644
index 0000000000000000000000000000000000000000..068f60ed73bc02974ad85cb7b2a985121680d1bc
--- /dev/null
+++ "b/data/1.MySQL\345\210\235\351\230\266/4.\346\225\260\346\215\256\347\261\273\345\236\213/2.\346\227\245\346\234\237\345\222\214\346\227\266\351\227\264\347\261\273\345\236\213/datetime.json"
@@ -0,0 +1,7 @@
+{
+  "type": "code_options",
+  "author": "Mars",
+  "source": "datetime.md",
+  "notebook_enable": false,
+  "exercise_id": "9f51c5816b1047368bdab70cb20d5116"
+}
\ No newline at end of file
diff --git "a/data/1.MySQL\345\210\235\351\230\266/4.\346\225\260\346\215\256\347\261\273\345\236\213/2.\346\227\245\346\234\237\345\222\214\346\227\266\351\227\264\347\261\273\345\236\213/datetime.md" "b/data/1.MySQL\345\210\235\351\230\266/4.\346\225\260\346\215\256\347\261\273\345\236\213/2.\346\227\245\346\234\237\345\222\214\346\227\266\351\227\264\347\261\273\345\236\213/datetime.md"
new file mode 100644
index 0000000000000000000000000000000000000000..a9d9aeb70624d8b2ceda8a304d0c285e5937edcd
--- /dev/null
+++ "b/data/1.MySQL\345\210\235\351\230\266/4.\346\225\260\346\215\256\347\261\273\345\236\213/2.\346\227\245\346\234\237\345\222\214\346\227\266\351\227\264\347\261\273\345\236\213/datetime.md"
@@ -0,0 +1,82 @@
+# 时间默认值
+
+Joe 写了一个订单表的创建语句：
+
+```mysql
+create table orders (
+    id int primary key auto_increment,
+    item_id int,
+    amount int,
+    unit_price decimal(12, 4),
+    total_price decimal(12, 4)
+);
+```
+
+现在，Joe 需要给这个表加入下单时间，即订单写入数据库的时间，那么他应该将这个语句修改为：
+
+## 答案
+
+```mysql
+create table orders (
+    id int primary key auto_increment,
+    item_id int,
+    amount int,
+    unit_price decimal(12, 4),
+    total_price decimal(12, 4),
+    ts timestamp default now()
+);
+```
+
+## 选项
+
+### A
+
+```mysql
+create table orders (
+    id int primary key auto_increment,
+    item_id int,
+    amount int,
+    unit_price decimal(12, 4),
+    total_price decimal(12, 4),
+    ts varchar(16) default now()
+);
+```
+
+### B
+
+```mysql
+create table orders (
+    id int primary key auto_increment,
+    item_id int,
+    amount int,
+    unit_price decimal(12, 4),
+    total_price decimal(12, 4),
+    ts varchar(16) format 'yyyy-mm-dd'
+);
+```
+
+### C
+
+```mysql
+create table orders (
+    id int primary key auto_increment,
+    item_id int,
+    amount int,
+    unit_price decimal(12, 4),
+    total_price decimal(12, 4),
+    ts date default now()
+);
+```
+
+### D
+
+```mysql
+create table orders (
+    id int primary key auto_increment,
+    item_id int,
+    amount int,
+    unit_price decimal(12, 4),
+    total_price decimal(12, 4),
+    ts datetime default now()
+);
+```