I am trying to create TablePrefixEventListener from medium.com. Everything works almost perfectly. Generated migration contains DROP TABLE and CREATE TABLE.
Now the model situation is this: The web project is set and everything works for let's say a year. Many data are in the table. For a reason there will be decision to change the prefixes. Is there a way how to explain to the Listener that it should first create the table, migrate the data and then drop the old table?
Related
I've a clustered partitioned table exported from GA 360. Attached is the image. I would like to create exact replica of the same. Using Web UI it's not possible. I created backup table using bq command line tool, still no luck.
Also, whenever we check preview it has a day filter. It looks like this:
Whenever data is appended to the backup table, I don't find this filter there even though this option is set to true while creating a table.
If you can give more context about handling this kind of table it would be beneficial.
Those are indeed sharded tables. As explained by #N. L they follow a time-based naming approach: [PREFIX]_YYYYMMDD. They then get grouped together. The explained procedure to backup them seems correct. Anyhow, I would recommend to use partitioned tables as it will be easier to backup them and they perform better in general.
This is not a cluster / partitioned table. This one is a sharded non-partitioned table having one common prefix. Once you start creating multiple tables with same prefix we can see them under the same prefix.
Ex:
ga_session_20190101
ga_session_20190102
both these tables will be grouped together.
To take backup of these tables you need to create a script to copy source to destination table with same name and execute that script using bq command line tool under the same project.
I have seen several members on this forum warn about creating tables in a database while the app is running. Instead it is encouraged to create the tables while programming, and only fill the tables with data during runtime.
E.g while creating a note-app it would be convenient to let the user specify a name for a single note, and let this note be created as a table in a database. This by creating the table at the time the user creates the note, and letting the name of the note be the name of the table. Why would this be a bad practise? Have I misunderstood?
It would be highly inconvenient for both you and the user of such an app to create a table for every note the user might want to add. It's just not the way it works. A table should contain rows of information of the same type, such as a note for example, and each note should be added as a row/record in the said table. The table should be called notes for example, and if you want a name for each note, it can be a column in the notes table called name.
An analogy would be, if you are taking notes manually (without an electronic device that is), would you have one notebook with you and just add notes on different pages as you need to, or would you carry around a bag full of notebooks so that whenever you want to add a new note, you would add each note in a separate notebook?
The notebooks being equivalent to database tables in this analogy, and the pages of the said notebook being equivalent to rows in a database table.
I can't think of a reason for creating tables during runtime really. The database structure should be "set in stone" so to speak, and during runtime you should only manipulate the data in the database, which is adding, deleting, or updating rows/records in already existing tables. Creating tables during runtime is a big no-no.
I probably don't understand your question correctly, but it seems to me, that what you really want to do is to create a new row in a table I the database?
Working on a SQLite database, seems DbVisualizer Pro does a lot of work very well, except one,
Changing table schema.
I often need to change column name, data type, etc, but don't want to do it through raw SQL statement. My workaround is opening Firefox's SQLite Manager to just change the schema.
Is it possible to use DbVisualizer to change the schema? many thanks!
Edit:
Alter table action mentioned below by roger, seems to be the right way to go. But somehow I can only add column, the existing column appears to be read only.
Mine is DBVisualizer Pro Evaluation. Is non-Evaluation different?
Edit2:
Using SQLite Manager is sometimes dangerous, as warned below. just learned, renaming a column may cause the foreign key loss. but workaround is here
In DbVisualizer Pro there is the Alter Table action (and Create Table for creating new tables). Select the actual table you want to change in the Databases tab, right-click and chose Alter Table. In order for this to work you need DbVisualizer Pro and the Database Type for your connection must be set to either Auto Detect (recommended) or SQLite.
I am thinking about ways to manage a table naming issue for an application I'm planning.
Currently there is a table that contains raw materials (approximately 150 rows) and each row has about 20 columns mainly float-value numbers used for calculations. For reference, let's refer to this table as 'materials'.
As these number columns are periodically updated and some users may also wish to create custom versions, I will create a management utility that allows copy/edit of this material table but, crucially it will only allow "save as" under a new table name so that data is never destroyed.
Thus using an automated routine, I'll create 'materials_1", "materials_2" and so on. When a calculation is done in another part of the website, I will store the name of the materials table that was used for the calculation so in future there can be audits done to find where a result has come from.
Now... is it possible for me to do this in an entity framework / unit of work/ repository way (like John Papa's codecamper example) without me having to continually edit the datacontext and add the newly created table names? I can't see how I can pass in a variable to the repository interface that contains the specific table name, which will always be a 'materials' entity even though the physical table name varies?
Not sure how to word the question...
Basically, so far all my SQL stuff has been stored procedures and dumped into a gridview. The odd case where I had to perform an action based on a value (such as highlighting a row green if a certain value was true) were done as the gridview was rendering in one of the overrides.
Now however I have to do something far more complicated - pull three sets of data down, run a series of checks on all three and some date related checks and stuff, then populate a gridview with some of the items.
In logic terms, I want to run three queries, and store the lists of results (presumably in Lists?) then run some logic, then populate the gridview.
Specifically what I don't know how to do is:
Best way of pulling the data, and putting it into a List or other datastructure that lets me easily run through it, and retrieve data based on column (myList.age, or more likely, myList["Age"]).
One I have compared the data, I assume I create a new list that will be put into the gridview... how do I put the contents of a list INTO a gridview? How would I add other stuff such as buttons or checkboxes at the same time?
Any nudge in the right direction would be appreciated! Particularly doing cool stuff with lists and sql (if there is anything cool you can do with them)
There are actually several ways to do this with .Net without using an ORM solution. Instead trying to list all of them here I will link you to an article series that should help you accomplish what you want. The following series of articles is about N-Layer design, and includes answers to the information you are looking for. The first set of 4 articles were created some time ago with ASP.Net 2.0 then the author updated them with an additional six articles using ASP.Net 3.5
http://imar.spaanjaars.com/QuickDocId.aspx?quickdoc=476
If you want to avoid having to write SQL query and concentrate on the data instead, go with the Entity Framework. It's quite well integrated with VS. It will connect to your SQL database, you will tell it which tables to import, and it will create a series of classes for you to talk to your database.
Queries are quite easy to do, and they will return lists of objects which should be easy to manipulate and put to a grid later on.
You can create datatables and populate them using the lists that you have generated and then bind your grid using the newly created tables as the datasource.