0
试图查看列中的内容我最终做了一些计数。列数为空加外加数不为零不加积分
该表格有3981行。
但是,已计数的列只显示其空值和非空值的总数要低得多。
怎么回事?
MariaDB [mydb]> select count(naf) from client where naf is not null;
+------------+
| count(naf) |
+------------+
| 83 |
+------------+
1 row in set (0.01 sec)
MariaDB [mydb]> select count(naf) from client where naf is null;
+------------+
| count(naf) |
+------------+
| 0 |
+------------+
1 row in set (0.01 sec)
MariaDB [mydb]> select count(*) from client;
+----------+
| count(*) |
+----------+
| 3981 |
+----------+
1 row in set (0.01 sec)