如何选择特定数据 [英] How to select spesific data

问题描述

首先我使用Access数据库和ole db conn。



我有桌子预订：



+ ------------ + -------------- +

| no_booking | date_service |

+ ------------ + -------------- +

| AN02091701 | 02/09/2017 |

| AN02091702 | 02/09/2017 |

| AN02091703 | 02/09/2017 |

| AN02091703 | 02/09/2017 |

| AN03091701 | 03/09/2017 |

| AN03091702 | 2017/03/09 | ---？找到AN03091702

| AN04091701 | 04/09/2017 |

| AN04091702 | 04/09/2017 |

| AN05091701 | 05/09/2017 |

| AN05091702 | 05/09/2017 |

| AN05091703 | 05/09/2017 |

| AN07091701 | 07/09/2017 |

+ ------------ + -------------- +



我想要预订服务..



我正在使用日期选择器来选择日期作为请求成员（确切地是随机的）。 。



我想要的条件 - >在一天内只有< 4 no_booking



接下来我试着找到有< b的日期4 no_booking自动创建no_booking。



假设我们现在没有日期所在的位置< 4 no_booking ...



如何找到包含< 4 no_booking（日期是03/09/2017因为有2个no_booking），



然后在03/09/2017选择no_booking的lastindex ----> ;完全是AN03091702。使用最快的查询？



希望我解释正确，但对不起我的英语..



谢谢。 ...



我的尝试：

first I'm using Access database and ole db conn.

I have table Booking :

+------------+--------------+
| no_booking | date_service |
+------------+--------------+
| AN02091701 | 02/09/2017 |
| AN02091702 | 02/09/2017 |
| AN02091703 | 02/09/2017 |
| AN02091703 | 02/09/2017 |
| AN03091701 | 03/09/2017 |
| AN03091702 | 03/09/2017 | ---? find AN03091702
| AN04091701 | 04/09/2017 |
| AN04091702 | 04/09/2017 |
| AN05091701 | 05/09/2017 |
| AN05091702 | 05/09/2017 |
| AN05091703 | 05/09/2017 |
| AN07091701 | 07/09/2017 |
+------------+--------------+

I want make bookingservice ..

i'm using date picker to select date as request member (exactly will be randomly)..

condition that i want --> in one day only have < 4 no_booking

next i try to find the date which have < 4 no_booking to create no_booking automatic.

assumtion that we don't now where the date have < 4 no_booking ...

how to find the top date that contain < 4 no_booking ( the date is 03/09/2017 because have 2 no_booking),

then select the lastindex of no_booking in 03/09/2017 ----> exactly AN03091702 . using fastest query ?

Hope I explain correctly,but sorry about my english ..

Thanks ....

What I have tried:

select no_booking,datebo from booking group by no_booking,datebo having count (datebo) < 3 

推荐答案

如果只需要选择包含特定值的列你必须使用 WHERE 子句：

If you need to select only columns containing a specific value you must use a WHERE clause:

SELECT nobooking,datebo FROM booking WHERE nobooking='AN30081702' GROUP BY nobooking,datebo HAVING COUNT(datebo) < 3;

如果列名包含空格（No Booking而非nobooking）或一段时间，你必须用引号或括号括起来。如果要返回表中的所有列，还可以使用 * 占位符：

If the column name contains a space ("No Booking" instead of "nobooking") or a period, you have to enclose it by quotes or brackets. If you want to return all columns from a table, you can also use the * placeholder:

SELECT * FROM booking WHERE [No booking]='AN30081702' GROUP BY [No booking],[datebo.] HAVING COUNT([datebo.]) < 3;

正如您所见，在数据库表和列中使用空格和点是个坏主意名。如果可能，请避免使用它们（以及SQL关键字）作为名称。

As you can see it is a bad idea to uses spaces and dots in database table and column names. Avoid them (and SQL keywords too) as names if possible.

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