functions for date and time

data/2.MySQL中阶/3.内置函数/5.时间日期函数/config.json

 {
   "node_id": "mysql-a7006c27131d4b87817a59717db7021c",
-  "keywords": [],
+  "keywords": [
+    "datetime",
+    "timestame",
+    "date",
+    "time",
+    "year",
+    "month",
+    "day",
+    "hour",
+    "minute",
+    "second",
+    "microsecond"
+  ],
   "children": [],
   "export": [
     "day.json",
@@ -8,7 +20,10 @@
     "weekofyear.json",
     "weekday.json",
     "to_days.json",
-    "now.json"
+    "now.json",
+    "extract.json",
+    "timestamp.json",
+    "from_days.json"
   ],
   "keywords_must": [],
   "keywords_forbid": [],

data/2.MySQL中阶/3.内置函数/5.时间日期函数/curtime.json

 {
   "type": "code_options",
-  "author": null,
+  "author": "ccat",
   "source": "curtime.md",
   "notebook_enable": false,
   "exercise_id": "bc88844a66244492947e98da40709619"

data/2.MySQL中阶/3.内置函数/5.时间日期函数/extract.json

+{
+  "type": "code_options",
+  "author": "ccat",
+  "source": "extract.md",
+  "notebook_enable": false,
+  "exercise_id": "73635de953474af4aa1af6cd90dc8129"
+}
\ No newline at end of file

data/2.MySQL中阶/3.内置函数/5.时间日期函数/extract.md

+# EXTRACT
+
+关于 Extract 操作和其它日期时间函数的对应关系，下列说法正确的是：
+
+1. `extract(mirosecond from date)` 相当于 `ms(date)`
+2. `extract(second from date)` 相当于 `second(date)`
+3. `extract(minute from date)` 相当于 `minute(date)`
+4. `extract(hour from date)` 相当于 `hour(date)`
+5. `extract(day from date)` 相当于 `day(date)`
+6. `extract(week from date)` 相当于 `week(date)`
+7. `extract(month from date)` 相当于 `month(date)`
+8. `extract(year from date)` 相当于 `year(date)`
+
+## 答案
+
+```
+2, 3, 4, 5, 6, 7, 8
+```
+
+## 选项
+
+### A
+
+全部都对
+
+### B
+
+```
+1, 2, 3, 4
+```
+
+### C
+
+全都不对
+
+### D
+
+```
+5, 6, 7, 8
+```
\ No newline at end of file

data/2.MySQL中阶/3.内置函数/5.时间日期函数/from_days.json

+{
+  "type": "code_options",
+  "author": "ccat",
+  "source": "from_days.md",
+  "notebook_enable": false,
+  "exercise_id": "cda783def29f4431979121e05498690c"
+}
\ No newline at end of file

data/2.MySQL中阶/3.内置函数/5.时间日期函数/from_days.md

+# FROM_DAYS
+
+FROM_DAYS 函数返回的是？
+
+## 答案
+
+给定从 0000 年 1 月 1 日起的天数，返回对应的日期
+
+## 选项
+
+### A
+
+给定从 1970 年 1 月 1 日起的天数，返回对应的日期
+
+### B
+
+都不对
+
+### C
+
+给定从当前日期算起的天数，返回对应的日期
+

data/2.MySQL中阶/3.内置函数/5.时间日期函数/timestamp.json

+{
+  "type": "code_options",
+  "author": "ccat",
+  "source": "timestamp.md",
+  "notebook_enable": false,
+  "exercise_id": "680153b527564dffaa026c8130e388f3"
+}
\ No newline at end of file

data/2.MySQL中阶/3.内置函数/5.时间日期函数/timestamp.md

+# TIMESTAMP
+
+关于 UNIX 时间戳和 MySQL 的日期时间类型，以下说法正确的是：
+
+1. UNIX_TIMESTAMP(date) 函数将 date 转换为 UNIX 时间戳
+2. FROM_UNIXTIME(timestamp) 将 UNIX 时间戳 timestamp 转换为 date 类型 
+3. extract(timestamp from date) 可以将 date 转换为 Unix 时间戳
+4. extract(datetime from timestamp) 可以将时间戳转换为 datetime
+
+## 答案
+
+```
+1, 2
+```
+
+## 选项
+
+### A
+
+全部都对
+
+### B
+
+全都不对
+
+### C
+
+```
+3, 4
+```
+