I have an access database that I need to update only if my information is unique. Is there a simple sql statement to accomplish this? Will 'insert ignore' work with access?
Example: I have the info stored in an array ('bob','34','hair'). If my database contains a record that matches on those three columns I would not want it to be inserted. If it was found to be unique I would like it to be inserted.
I am writing this in cold fusion but just cant seem to get the sql right.
Before doing an insert, do a select for those values. If you don't get a record back then you know it is safe to insert. Just use two separate queries, one for the check, and if no record found, then the insert.
A unique index is always a good idea if a field or set of fields should be unique. If you have a unique index in Access on the three fields, an insert will fail.
It is possible is to create a single query that only inserts a record where a matched record is not found, for example:
INSERT INTO Shows (ForeName,Reviews,Musical)
SELECT "bob" As ForeName,"34" As Reviews,"hair" As Musical
FROM (SELECT Count(*) As ExistsCount
FROM Shows
WHERE ForeName = "bob",Reviews = "34",Musical = "hair") AS e
WHERE e.ExistsCount=0
Related
I have a database table which constantly gets updated. I am looking to query only the changes/additions that have been made on rows with a specific attribute in a column. e.g. get the rows which have been changed/added, the 'description' column of which is "xyz". My end goal is to copy these rows to another table in another database. Is this even possible? The reason for not just querying and overwriting the rows in the other database is to avoid inefficiency.
What I have tried so far?
I am able to select query on the table to get the rows but it gives me all the rows, not the ones that have been changed or recently added. If i add these rows to the table in the other database, the only option I have is to overwrite the rows.
Log table logs the changes in a table but I can't put additional filters in SQL which tells me which of these changes are associated with 'description' column as 'xyz'.
Write your update statements to make use of OUTPUT to capture the before and after values and log them to a table of your choice.
Here is a really simple example update example that uses output to store the RowID, before and after values for the ActivityType column:
DECLARE #MyTableVar table (
SummaryBefore nvarchar(max),
SummaryAfter nvarchar(max),
RowID int
);
update DBA.dbo.dtest set ActivityType = 3
OUTPUT deleted.ActivityType,
inserted.ActivityType,
inserted.RowID
INTO #MyTableVar
select * From #MyTableVar
You can do it two ways
Have new date fields/columns like update_time and/or create_time(Can be defaulted if needed). These fields will indicate the status of the record. You need to save your previous_run_time and then your select query will look for records with update_time/create_time greater than previous_run_time, and then you can move these records to the new DB.
Have CDC turned on the source table, which is available by default in SQL server and then move only those records that have been impacted.
i am trying to copy table information from a backup dummy database to our live sql database(as an accident happened in our program, Visma Business, where someone managed to overwrite 1300 customer names) but i am having a hard time figuring out the perfect code for this, i've looked around and yes there are several similar problems, but i just can't get this to work even though i've tried different solutions.
Here is the simple code i used last time, in theory all i need is the equivilant of mysqls On Duplicate, which would be MERGE on SQL server? I just didn't quite know what to write to get that merge to work.
INSERT [F0001].[dbo].[Actor]
SELECT * FROM [FDummy].[dbo].[Actor]
The error message i get with this is:
Violation of PRIMARY KEY constraint 'PK__Actor'. Cannot insert duplicate key in object 'dbo.Actor'.
What error message says is simply "You cant add same value if an attribute has PK constraint". If you already have all the information in your backup table what you should do is TRUNCATE TABLE which removes all rows from a table, but the table structure and its columns, constraints, indexes, and so on remain.
After that step you should follow this answer . Or alternatively i recommend a tool called Kettle which is open source and easy to use for these kinds of data movements. That will save you a lot of work.
Here are thing which can be the reason :
You have multiple row in [FDummy].[dbo].[Actor] with same data in a column which is going to be inserted in primary key column of [F0001].[dbo].[Actor].
You have existing rows in [FDummy].[dbo].[Actor] with some value x in primary key column and there is/are row(s) in [F0001].[dbo].[Actor] with same value x in the column which is going to be inserted in primary key column.
List item
-- to check first point. if it returns row then you have some problem
SELECT ColumnGoingToBeMappedWithPK,
Count(*)
FROM [FDummy].[dbo].[Actor]
GROUP BY ColumnGoingToBeMappedWithPK
HAVING Count(*) > 1
-- to check second point. if count is greater than 0 then you have some problem
SELECT Count(*)
FROM [FDummy].[dbo].[Actor] a
JOIN [F0001].[dbo].[Actor] b
ON a.ColumnGoingToBeMappedWithPK = b.PrimaryKeyColumn
The MERGE statement will be possibly the best for you here, unless the primary key of the Actor table is reused after a previous record is deleted, so not autoincremented and say record with id 13 on F0001.dbo.Actor is not the same "actor" information as on FDummy.dbo.Actor
To use the statement with your code, it will look something like this:
begin transaction
merge [F0001].[dbo].[Actor] as t -- the destination
using [FDummy].[dbo].[Actor] as s -- the source
on (t.[PRIMARYKEY] = s.[PRIMARYKEY]) -- update with your primary keys
when matched then
update set t.columnname1 = s.columnname1,
t.columnname2 = s.columnname2,
t.columnname3 = s.columnname3
-- repeat for all your columns that you want to update
output $action,
Inserted.*,
Deleted.*;
rollback transaction -- change to commit after testing
Further reading can be done at the sources below:
MERGE (Transact-SQL)
Inserting, Updating, and Deleting Data by Using MERGE
Using MERGE in SQL Server to insert, update and delete at the same time
I have two tables in my database, one is Transactions and the other is TransactionHistories. The latter is essentially an auditing table, whereby a trigger executes on insert, update and delete on Transactions to capture a screenshot of the data.
I am successfully retrieving all of the data stored in the Transactions table where the columns match, but the difficulty comes where I am trying to retrieve data from another table using a foreign key. For instance:
The transaction table has a field "TransactionType_TransactionTypeId", but in the audit table we wish to store its 'name' equivalent as "TransactionTypeName". This needs to be populated from the "TransactionTypes" table, which has the fields "TransactionTypeId" and "Name".
I am struggling to write a query to retrieve this as we wish. I am trying something similar to the following but having little success:
SELECT #TransactionTypeName=Name
FROM TransactionTypes
WHERE inserted.TransactionType_TransactionTypeId=TransactionTypes.TransactionTypeId;
I'm assuming that is a syntactic nightmare. If someone could point me in the right direction I would be extremely grateful!
well to get a name you should do the following
select #TransactionTypeName = TT.Name
from inserted as i
left outer join TransactionTypes as TT on TT.TransactionTypeId = i.TransactionType_TransactionTypeId
but you have to know that inserted table can have more than one row, and you are getting value for only one row.
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.
What would be the correct universal SQL construct to get the last row inserted (or it's primary key). The ID might be autogenerated by a sequence but I do not want to deal with the sequence at all! I need to get the ID by querying the table. Alternatively, INSERT might be somehow extended to return the ID. Assume I am always inserting a single row. The solution should work with most RDBMS!
the best way is to depend on the sequence like:
select Max(ID) from tableName
but If you don't want to deal with it, you can add new timestamp column to your table and then select max from that column.
like this way
select Max(TimestampField) from tableName