cursor

data/3.MySQL高阶/4. 过程化编程/5. 游标/config.json

 {
   "node_id": "mysql-459fd14ff096438d9b6460270bec4754",
-  "keywords": ["cursor"],
+  "keywords": [
+    "cursor",
+    "游标"
+  ],
   "children": [],
-  "export": [],
+  "export": [
+    "cursor.json"
+  ],
   "keywords_must": [],
   "keywords_forbid": [],
   "group": 0

data/3.MySQL高阶/4. 过程化编程/5. 游标/cursor.json

+{
+  "type": "code_options",
+  "author": "ccat",
+  "source": "cursor.md",
+  "notebook_enable": false,
+  "exercise_id": "106eadb83e2c4928b503d89dda2dd8f3"
+}
\ No newline at end of file

data/3.MySQL高阶/4. 过程化编程/5. 游标/cursor.md

+# 游标
+
+Joe 需要开发一个存储过程 make_trade，从 orders 表
+
+```mysql
+create table orders (
+    id int primary key auto_increment,
+    price decimal(12, 4),
+    item_id int,
+    amount int
+)
+```
+
+中，按 id 从小到大加载订单数据，生成交易单，写入 trade 表 
+
+```mysql
+create table trade (
+    id int primary key auto_increment,
+    total decimal(12, 4)
+    -- ...
+)
+```
+
+其中 trade 的 total字段保存了交易单的总金额，这个金额是每一张交易单的所有 orders 的 price 总和，其数值不会超过 20000。
+
+因为撮合交易的逻辑是串行的，Joe决定用游标实现这部分逻辑。下列哪一个选项是对的(选项中仅包含撮合逻辑，不包括完整的存储过程)？
+
+为简单起见，我们忽略交易的详细逻辑，假设 orders 表仅包含 id, price, item_id, amount 四项。
+
+## 答案
+
+```mysql
+create procedure make_trade()
+begin
+    DECLARE done INT DEFAULT FALSE;
+    declare cur_orders cursor for select id, price, item_id, amount from orders order by id limit 1000;
+    declare order_id, item_id, amount INT;
+    declare price decimal(12, 4);
+    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;
+    
+    open cur_orders;
+    trade: LOOP
+        fetch cur_orders into order_id, price, item_id, amount;
+        if done then
+            LEAVE trade;
+        end if;
+    if @total + @price > 2000 then
+        leave trade;
+    else
+        -- 省略交易逻辑        
+    end if;
+    END LOOP trade;
+    CLOSE cur_orders;
+    start transaction;
+    -- save trade
+    delete from orders where id < order_id;
+    commit ;
+
+end;
+```
+
+## 选项
+
+### A
+
+```mysql
+create procedure make_trade()
+begin
+    DECLARE done INT DEFAULT FALSE;
+    declare cur_orders cursor for select id, price, item_id, amount from orders order by id limit 1000;
+    declare order_id, item_id, amount INT;
+    declare price decimal(12, 4);
+    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;
+    
+    open cur_orders;
+    trade: LOOP
+        fetch cur_orders into order_id, price, item_id, amount;
+        if done then
+            LEAVE trade;
+        end if;
+    -- 省略交易逻辑
+    if @total + @price > 2000 then
+        leave trade;
+    else
+        NEXT cur_orders;
+    end if;
+    END LOOP trade;
+end;
+```
+
+### B
+
+```mysql
+create procedure make_trade()
+begin
+    declare cur_orders cursor for select id, price, item_id, amount from orders order by id limit 1000;
+    declare order_id, item_id, amount INT;
+    declare price decimal(12, 4);
+    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;
+    
+    trade: LOOP
+        fetch cur_orders into order_id, price, item_id, amount;
+    -- 省略交易逻辑
+    END LOOP trade;
+    start transaction;
+    -- save trade
+    delete from orders where id < order_id;
+    commit ;
+end;
+```
+
+### C
+
+```mysql
+create procedure make_trade()
+begin
+    DECLARE done INT DEFAULT FALSE;
+    declare cur_orders cursor for select id, price, item_id, amount from orders order by id limit 1000;
+    declare order_id, item_id, amount INT;
+    declare price decimal(12, 4);
+    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;
+    
+    open cur_orders;
+    fetch cur_orders into order_id, price, item_id, amount;
+    if done then
+        LEAVE cur_orders;
+    end if;
+    -- 省略交易逻辑
+    
+end;
+```
+
+### D
+
+```mysql
+create procedure make_trade()
+begin
+    DECLARE done INT DEFAULT FALSE;
+    declare cur_orders cursor for select id, price, item_id, amount from orders order by id limit 1000;
+    declare order_id, item_id, amount INT;
+    declare price decimal(12, 4);
+    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;
+    
+    open cur_orders;
+    trade: LOOP
+        fetch cur_orders into order_id, price, item_id, amount;
+        if done then
+            LEAVE trade;
+        end if;
+    -- 省略交易逻辑
+        
+    END LOOP trade;
+    CLOSE cur_orders;
+    start transaction;
+    -- save trade
+    delete from orders where id < order_id;
+    commit ;
+end;
+```
\ No newline at end of file

data/tree.json

@@ -2180,7 +2180,10 @@
                   {
                     "REPEAT": {
                       "node_id": "mysql-923c7bbf96cf4630a5dfb36f15e62d24",
-                      "keywords": [],
+                      "keywords": [
+                        "repeat",
+                        "循环"
+                      ],
                       "children": [],
                       "keywords_must": [],
                       "keywords_forbid": [],
@@ -2203,7 +2206,8 @@
                     " 游标": {
                       "node_id": "mysql-459fd14ff096438d9b6460270bec4754",
                       "keywords": [
-                        "cursor"
+                        "cursor",
+                        "游标"
                       ],
                       "children": [],
                       "keywords_must": [],