Recently I have been using Microsoft SQL for creating databases that are referred to using an excel document. There have been a number of instances when I needed to make a small changes to my tables and ended up "DROP"-ing all my current tables and re-creating them using an updated query. I understand you can use UPDATE to change the values of records within a table, but I'm looking to manipulate a data type so that I can change the number of decimals in one record of my tables from 2 to 3. Code for creating the table looks something like this:
CREATE TABLE WIRE_INDEX
--"Field" "Data Type" "Null or Not"
(...
...
DENSITY decimal(18,2) Not Null);
I don't know if the solution is something obvious, but I have been unable to find anything useful. I'm not sure know how to refer to the data type of a field in SQL.
When I populate the database I use numbers like 0.283 and 0.164, but when I SELECT the record I only get the first two decimals. I'd like the first 3 decimals to appear in the way I enter them into the table.
(edit didn't show up properly)
(not sure if I'm supposed to post my solution), but credit to TEEKAY and Apurav for answering my question. I used the code posted by Apurav which looks like this:
ALTER TABLE WIRE_INDEX
ALTER COLUMN DENSITY decimal(18,3) Not Null
When I pulled the table, using a SELECT statement the precision showed three decimal places, but I lost the precision of my input and had to re-enter my values using UPDATE. Not sure if this is more effective than just starting over, but it worked for me and now I know.
Related
I need some help and I know I am not the only one to deal with this issue but I am wondering if you might have some ideas on how to handle the situation of comparing two rows of data filling out start and end dates.
To give you some context, we have a huge hierarchy (approx 8,000 rows and about 12 columns wide) that is updated each year. Sometimes the values change and sometimes they don’t. When the values don’t change, then I don’t need to adjust the dates. When the values do change and a new row is added, I need to change the data.
I have attached some fake data to try and illustrate my data. I am building this in MS Access, so I think this is more of a DBA type question that is going to be manipulated via a recordset type method.
In my example I have two tables – Old Table and New Table. In each table there is a routing code field that represents my join field and primary key for this table.
The Old table represents existing data - tblMain. The New Table represents the data to be appended - tblTemp.
To append the data, I have an append query set up in Access. I perform a left join between the Old and New tables, joining on every field and append the rows that are null in the Old table. That’s fine and that is not where my issue is.
What is causing me issue is how to fill out the start and end dates.
So as you can see from my tables, we are running a zoo. Let’s just say for the sake of the argument, our zoo started off pretty simple and has become more sophisticated. We now want our hierarchy to expand out and become a bit more detailed as we are now capturing the type of animal (Level 4) and the native location (Level 5).
As you can see when comparing one table to another the routing codes are the same, so the append query has to have a join on each field. When you do this, you return the Result Table which is essentially the Old and New tables stacked on top of each other. You might think about a Union query but this is going to give me duplicates and I don’t want that.
If you notice in the Result Table there is a Start and End Date. Let’s just say I get the start and end dates via message box that pops up upon the import of the data and is held in a variable. I think there are dates in my real data but still trying to verify this.
So how do I compare (pseudo code for the logic needed)?
• For each routing code:
Compare Levels 1-5
If the routing code is the same but Levels 1 -5 are not the same
fill out the end date of the old record
fill out the start date of the new record
This idea of comparing two records and filling out a data is quite prevalent in my organization but I haven’t found a way of creating the logic that consistently works so any help or suggestions would be appreciated.
Old Table
New Table
Result Table
I understand this is probably a really REALLY silly problem, but I've only just started using SQL since Monday. Originally I was using an access database and converted it to SQLExpress and now I'm getting that error. Included are some screenshots that will hopefully show you how I've messed up.
The Query
The Database in SQL Studio
When you are doing an insert in Sql you need to either provide a list of the columns you are inserting into or provide values for all columns in the table.
Since your insert is providing one value and your table has two columns you would need to provide a list containing the column for which you are providing values.
insert into Data$ (CompItemNo)
Select CompItemNo
From Kits$
where ItemNo = :ItemNo;
I don't know the best way to describe my problem and I'm just looking for a push in the right direction, or where to start. I'd be perfectly happy with an answer that's a very useful link or pseudo code.
My problem, I have a database that's about to hit the MS Access hard coded 2 GB database limit and I don't want to split the database.
What I think is a possible solution - make the database more efficient in it's data storage. I think, but don't know if this is true, that I could do this by turning some string fields into numeric fields. Stay with me...
For instance:
My database has several million records of a field we'll call TooLongString
Each value is about 50 characters
Every record has a value for this field
There's only 9 possible values for TooLongString
Would it decrease my database size to instead store a number that
represents one of the 9 possible values and store the text value in a small table? (So go from 50 characters to 1 character several million times)
Did I explain my issue correctly? Is my potential solution actually a solution? How would I go about doing this?
Thanks!
The short answer is yes, that would reduce the size of your database. You could have a second table that holds the nine possible values for "TooLongString" and just store the ID of the appropriate answer in the main table, as you suggested. You would then need to join these tables when pulling the data out in order to retrieve the actual text instead of the ID.
I would set up your new table first, then add a new column for the ID into your existing one. As there are only nine possible values, I'd be tempted to just manually run an UPDATE query nine times, e.g. if the first string in your new table is "MyFirstString" with ID 1, you could run "UPDATE existingTableName SET newColumn = 1 WHERE oldColumn = 'MyFirstString'". Do this for each of the nine values then you can remove the old string column from your table at the end.
In my Access database, I have a table called customers. In this table I have a column called DateEntered. The data type for the field is short text.
The values in this column are not coherent - they come in several variations:
MM-DD-YYYY,
MMDDYYYY and
MM/DD/YYYY.
There doesn't seem to be any standard set.
My goal is to select all customers from 2012. I tried
select *
from customers
where DateEntered <('%2013') AND >('%2012');
but it comes up blank when I run it.
Can anyone point out what I'm failing to do correctly & more importantly explain why exactly this query doesn't work in Access? From my understanding of SQL (not very advanced) this should work.
Another variant)
select * from customers where RIGHT(DateEntered, 4) = '2012'
If you have control over the database and application code, the best way to handle this is to use an actual Date field instead of text in the table.
One way to handle this would be to add a new field to the table, write a query or two to correctly convert the text values to actual date values, and populate the new field.
At this point, you would then need to hunt down the application code the refers to this field in any way and adjust to treat the field as a date, not text. This includes your insert and update statements, report code, etc.
Finally, as a last step, I would rename the original text field (or remove it altogether) and rename the new date field to the original field name.
Once you fix the problem, querying against the field will be a piece of cake.
Alternatively, if you can't alter the table and source code, you can use the date conversion function CDATE() to convert the text value to an actual date. Note that you may need to guard against non-date entries (NULL or empty string values, as well as other text values that aren't really dates in the first place). The IsDate() function can be your friend here.
If you have the time and patience, fixing the data and code is the better approach to take, but sometimes this isn't always feasible.
Why don't you use LIKE operators (they're appropriate when you have a pattern using % and _):
select * from customers where DateEntered like '%2013' or DateEntered like '%2012'
This is with respect to search of a text in a table
Table_Name:
Details
Columns:
Fname,Mname,Lname,NName
This table contains nearly one lakh records
We are using Oracle forms for some querying option
The user input one name the form searches the table for the name and based on the name either(Fname/Mname/Lname/NName) in which column its is present further actions are proceeeded.
The search is taking a long time since we have huge amount of data present in the table.
I tried with Functional indexes for the table but t did not work its also taking more time
Later i tried with something like this
concatenated all the names into one name and put it into a cursor.
Using the cursor output i tried with Instring but it is hanging
I also tried with searching for building a dynamic cursor but it did not work.
My database is Oracle
Can u help me to out to find an effective solution or please help me if i have missed something.
Thanks
First of all, 1 lakh (100,000) records is not in itself a large table.
The problem I can see is the query appears to be doing an OR against the Fname/Mname/Lname/NName columns.
This means the query will be doing at least one full-table scan to obtain the results.
You may wish to use debug to obtain the query it is firing against the database and attempt to tune this at the SQL prompt using auto trace.
You may need to clarify if the search is also doing something like a LIKE against these columns rather than an EQUALS. As a LIKE will impact the query further and affect indexes.
Certainly the use of INSTR will disable indexes on your searched column.
It is not clear if what your block is based on ie. table, view, query, procedure
You may want to try using the hint on the block properties of the form FIRST_ROWS.