So I've got:
id number
1 0
2 0
3 0
Is there a sql statement to copy everything from id into number?
I'm about to write a php scrip to select, then update every row. My SQL knowledge is pretty basic, but I'm sure there's a smart guy way to to do this:
Background: The id used to be a number that was displayed in the app and was unique. That number is no longer unique with some new features I'm adding--so I need to move it to a field that isn't unique while maintaining the integrity of the old.
You can use an update statement and reference the columns. Just do the following:
update mytable set number = id
That sets number equal to id on each row. Enjoy!
Related
I have a item tax table that records the different tax rates for different counties in our state. Each row has an ID number (1-130). Our front end software always orders the tax options by this number when we want it alphabetical. Most of our rows were added that way but I want to be able to insert rows.
Thus I need to add 1 to every entry after a certain number (e.g. 37-130 need to all increase by one). Unfortunately, this is the primary key. Is it possible to increase this value on all of them easily? Or in a loop? I'll have to do this repeatedly as we're moving about a dozen entries if possible.
UPDATE ItemTax
SET ID = ID + 1
WHERE ID = Last ID number
Treating your question as academic, and not endorsing this as an actual solution, you can do this:
UPDATE ItemTax
SET ID = ID + 1
WHERE ID > 37
Depending upon how you use this id, it might be better to leave original ID column unchanged. E.g.
alter table TaxItem add NewID int null
GO
update TaxItem set NewID =
case
when ID between 37 and 130 then ID + 1
else ID
end
Now you don't have to update foreign key relationships, etc.
You see, as ID usually represents a surrogate key, and should never have its value changed in a good design. So your desire to change it value leads to suspicion that you do not understand your design as well as you should. -- We all start from ignorance, I have bad some very poor decisions in the past.
If this is the only change there will ever be for NewID, you don't even need a physical column, a computed column would serve well. But if this is the first mod of many a physical column is likely a better choice.
You also mention inserting rows. Build in some room to insert rows and change values as needed because you have room to rearrange rows by tweaking values without having to renumber entire blocks of rows just to insert a single row, e.g.
update TaxItem set NewID = ID * 100
Happy Holidays. I have two dependent tables, [orders] and [reviews], linked by a "one to many relationship". On the [Orders], the PK is [Order#], there is a column for [#_of_reviews_ordered]. On the [reviews] table (the PK is an auto number) the linked field is [order#] and the number of records (records on the table) should equal "[Orders].[#_of_reviews_ordered]".
Is there a simple way to accomplish this without having to do add the records to [reviews] manually?
The only way I can think to do this without VBA is fairly convoluted and would only work if your number of reviews orders fits within a finite (and reasonably small) range. For my explanation I will assume # of review will be between 0 and 3
You would need to create a table called, say, TemplateReviews. This would have at least one field called "KeyNumber", which should not actually be a key. You could also repeat as many fields as desired from Reviews, and use them to store default values for the rows to be inserted.
The important thing about TemplateReviews is that you must set it up in advance to have N rows with KeyNumber=N for each possible value of KeyNumber. For my example, we can have 0 to 3 # of reviews. So TemplateReviews will have:
0 rows with KeyNumber=0
1 row with KeyNumber=1
2 rows with KeyNumber=2
3 rows with KeyNumber=3
Once you have TemplateReviews set up, you need to create an Insert query based on it. The query will insert rows from TemplateReviews into Reviews. But you also have to filter KeyNumber to match the value on the currently selected Order, as in
=Forms!Orders![#_of_reviews]
You then need run Insert query to run using a macro triggered by a button (etc) on the Orders form. This only works the first time you click the button... but you can modify the criteria expression above to subtract the number of existing reviews, as in
=Forms!Orders![#_of_reviews] - DCount("*","Reviews","OrderId=" & Forms!Orders![order#])
Hope this helps. If you got this approach working, you could then replace the button with a single line of VBA code in the Order form AfterUpdate event to trigger the insert query.
For example, I have a table:
User ID(int) | Card ID(int) | Deck(int)
1841 | 14 | 1
1841 | 14 | 1
it is defined that the int values in deck column would always take on 1 or 2 as a value(1 indicating that it is in the deck). and card ID is not unique for a user(this indicate that a user have 2 card 14) , as shown in the example above. what if i want to remove one card 14 in the deck and the other would remain. what is the proper sql command, i tried UPDATE but it
you can define limit at the end of update query
update [table name] set Deck=2 where User_ID=1841 and Card_id=14 limit 1;
Basically you're missing a way of referencing any single particular row. Depending how critical to the application is need for such reference, it is almost always bad idea to allow such situation. There are many solutions for this, for example
1) Every row usually contains unique OID or ROWID field , which is not displayed with "SELECT * FROM TABLE", but can be used if requested implicitly. Depending on what database engine you use, e.g. with PostgreSQL try
SELECT OID, * FROM TABLE WHERE OID = 'somevalue'
this is usually used if you don't want to enforce UNIQUE on the table, but rather deal with possible mistaken input later if it will unfortunately appear.
2) You can add ID column, for example autoincremental ( refer to DB manual ), and then update it to contain unique IDs
ALTER TABLE table_name ADD column_name column-definition;
3) You can use self incrementing "running total", eg. with MySQL it looks more/less like this:
SET #runtot:=0;
SELECT *, (#runtot := #runtot + 1) AS rt FROM table WHERE rt='somevalue'
(this will do calculation every time so probably will be inefficient )
4) You can use LIMIT as explained in previous answer
5) You can JOIN some another table with unique IDs and possibly update resulting relation, or combine some query to create and use static VIEW
6) You can use SELECT with some dynamically allocated value, for example RAND() or NOW() or similar. It probably won't create unique identifiers across whole table, depending what function you'll use and how you will use it
7) combine two or more above solutions altogether
..and probably many other solutions. Anyway usually there's some "Id" column used with some UNIQUE constraint.
I have a table with 4 columns. The first column is unique for each row, but it's a string (URL format).
I want to update my table, but instead of using "WHERE", I want to update the rows in order.
The first query will update the first row, the second query updates the second row and so on.
What's the SQL code for that? I'm using Sqlite.
Edit: My table schema
CREATE table (
url varchar(150),
views int(5),
clicks int(5)
)
Edit2: What I'm doing right now is a loop of SQL queries
update table set views = 5, click = 10 where url = "http://someurl.com";
There is around 4 million records in the database. It's taking around 16 seconds in my server to make the update. Since the loop update the row in order, so the first query update the first row; I'm thinking if updating the rows in order could be faster than using the WHERE clause which needs to browse 4 million rows.
You can't do what you want without using WHERE as this is the only way to select rows from a table for reading, updating or deleting. So you will want to use:
UPDATE table SET url = ... WHERE url = '<whatever>'
HOWEVER... SqlLite has an extra feature - the autogenerated column, ROWID. You can use this column in queries. You don't see this data by default, so if you want the data within it you need to explicitly request it, e.g:
SELECT ROWID, * FROM table
What this means is that you may be able to do what you want referencing this column directly:
UPDATE table SET url = ... WHERE ROWID = 1
you still need to use the WHERE clause, but this allows you to access the rows in insert order without doing anything else.
CAVEAT
ROWID effectively stores the INSERT order of the rows. If you delete rows from the table, the ROWIDs for remaining rows will NOT change - hence it is possible to have gaps in the ROWID sequence. This is by design and there is no workaround short of re-creating the table and re-populating the data.
PORTABILITY
Note that this only applies to SQLite - you may not be able to do the same thing with other SQL engines should you ever need to port this. It would be MUCH better to add an EXPLICIT auto-number column (aka an IDENTITY field) that you can use and manage.
I have a table, and there is no column which stores a field of when the record/row was added. How can I get the latest entry into this table? There would be two cases in this:
Loop through entire table and get the largest ID, if a numeric ID is being used as the identifier. But this would be very inefficient for a large table.
If a random string is being used as the identifier (which is probably very, very bad practise), then this would require more thinking (I personally have no idea other than my first point above).
If I have one field in each row of my table which is numeric, and I want to add it up to get a total (so row 1 has a field which is 3, row 2 has a field which is 7, I want to add all these up and return the total), how would this be done?
Thanks
1) If the id is incremental, "select max(id) as latest from mytable". If a random string was used, there should still be an incremental numeric primary key in addition. Add it. There is no reason not to have one, and databases are optimized to use such a primary key for relations.
2) "select sum(mynumfield) as total from mytable"
for the last thing use a SUM()
SELECT SUM(OrderPrice) AS OrderTotal FROM Orders
assuming they are all in the same column.
Your first question is a bit unclear, but if you want to know when a row was inserted (or updated), then the only way is to record the time when the insert/update occurs. Typically, you use a DEFAULT constraint for inserts and a trigger for updates.
If you want to know the maximum value (which may not necessarily be the last inserted row) then use MAX, as others have said:
SELECT MAX(SomeColumn) FROM dbo.SomeTable
If the column is indexed, MSSQL does not need to read the whole table to answer this query.
For the second question, just do this:
SELECT SUM(SomeColumn) FROM dbo.SomeTable
You might want to look into some SQL books and tutorials to pick up the basic syntax.