提交 3dd3d652 编写于 作者: M Mars Liu

修正查询计数的答案错误

上级 79a63904
{
"node_id": "mysql-ac3c072bc54749bdb82324f2b203890d",
"keywords": ["count", "计数"],
"keywords": [
"count",
"计数"
],
"children": [],
"export": [
"count.json"
......
......@@ -33,7 +33,12 @@ from items;
## 答案
```
3, 4
+----------+-------------+
| count(*) | count(item) |
+----------+-------------+
| 4 | 3 |
+----------+-------------+
1 row in set (0.00 sec)
```
## 选项
......@@ -41,29 +46,54 @@ from items;
### A
```
4, NULL
+----------+-------------+
| count(*) | count(item) |
+----------+-------------+
| 4 | NULL |
+----------+-------------+
1 row in set (0.00 sec)
```
### B
```
3, 3
+----------+-------------+
| count(*) | count(item) |
+----------+-------------+
| 3 | 3 |
+----------+-------------+
1 row in set (0.00 sec)
```
### C
```
1, 0
+----------+-------------+
| count(*) | count(item) |
+----------+-------------+
| 4 | 4 |
+----------+-------------+
1 row in set (0.00 sec)
```
### D
```
NULL, NULL
+----------+-------------+
| count(*) | count(item) |
+----------+-------------+
| NULL | NULL |
+----------+-------------+
1 row in set (0.00 sec)
```
### E
```
4, 4
+----------+-------------+
| count(*) | count(item) |
+----------+-------------+
| 4 | 0 |
+----------+-------------+
1 row in set (0.00 sec)
```
\ No newline at end of file
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