I have a table called table books in Microsoft Access. In this table there is a field called availability which means the number of books up till now. My question is how to use update query to add number x to the value in field availability.
Update field in MS Access.
Related
In my MS Access database, some of my data have the same Date, Time and StationID but have a different value in the last field (Communication field)
MS ACCESS DATABASE
How can I choose a specific record with "VHF" in Communication field?
I try to use SELECT DISTINCT, but it removed the communication field from my query.
The DISTINCT function will return all rows with unique values in a specific column. What you are looking for is the WHERE clause:
SELECT * FROM myTable WHERE Communication = 'VHF'
The above will return only records with VHF in Communications.
I've a list of records (in excel) which I want to lookup in SQL table to find their entry date in table.
For example I've name of 200 customers in an excel sheet which are also in my SQL table but there are many others as well. I want to compare those users in table and find their date of joining the table i.e the date they were added to the table.
Do you have any column such as "customer_id"? If not, create it in the tables as it will make it easier for you to select and join tables. You can use the alter table statement to add the new column. After adding the columns, join the tables and use the select statement to find the required record.
You must have a key to bind those data. Any other way can be dangerous linking these informations. Maybe, the way is adapt your application or excel to provide this bind between the data.
I have table 1 with 4 columns. The 3rd Column was a lookup, and a value comes from table 2. Table 1, field 4 requires that one of Tables 5-8 is chosen as the lookup choices, not just one specific table. How do I filter to the correct table by using VBA or SQL?
Eg value in column 3 = BU. If the answer is AT, the correct table is XXX; if the answer is BU, the correct table is YYY, for column 4 lookup.
I want to get last inserted row id in mysql any one help me
Table field is
If you want to get the id just after the insertion, use LAST_INSERT_ID():
SELECT LAST_INSERT_ID();
This will return the AUTO_INCREMENT value of the last inserted element (in your current connection).
If you want to know which is the last inserted value in a determined table, use any of the queries provided in the other answers.
You can use LAST_INSERT_ID(), but you should be aware that (you not only should have the AUTO_INCREMENENT), but it does operates in at connection level. This is, it will return the last_insert_id() for the current connection and not the last_insert_id() that another connection --that might be happening meanwhile-- generated.
Example (lets say the operations arrive the database in the following order):
-Connection A : user A -> insert order (id = 1000), lets say $20
-Connection B : user B -> insert order (id = 1001), lets say $50
.... multiple orders from other users are placed
-Connection B : you retrieve last_insert_id (value 1001) and you retrieve the order amount, and update the user B profile with the total revenue generated (+$50).
-Connection A : you retrieve last_insert_id (value 1000) and you retrieve the order amount, and update the user A profile with the total revenue generated (+$20).
You should be aware that last-insert_id() operates on a connection level, therefore you want to keep the connection open until you are finished. You should not use things like do a max on the database, because on a web environment you don't have control on how many users will use your app at same time, and in which order the operations will be executed and most important you want to keep your database consistent.
I'm writing a formula in Access where I want to minus date in the current row to the date in the upper row in the same column. As I'm very new to Access, I'm not able to figure out how can I assign a cell reference to it.
For example, like in Excel, we can put cell reference =a3-a2, how can we do it in Access.
You cannot do that in Access. A database table is not worksheet. You can only work record-wise in a database. What you can do is to join the table to itself. But this works only if you have an appropriate field that tells you how the records are related, for instance like a record number
Table:
RecordNo, Date
The query goes like this
SELECT
DateDiff('d', t1.Date, t2.Date) As Days
FROM
myTable t1
INNER JOIN myTable t2
ON t1.RecordNo + 1 = t2.RecordNo
One basic rule in databases is that the table records have no natural order. I.e. they do not have a line number bound to them. The database engine can reorder the rows when the database is compacted. Therefore a table must always have a primary key that allows you to identify a record. If you need a specific order, you must have a column that reflects this order and that you can use in an ORDER BY clause in a query.