I have been trying to find out what happens in SharePoint when we select a column as index column? I mean what happens in back end(database level)? I tried many articles but they just say that it improves performance but they don't say how. I found this question and others related to performance but I couldn't get a complete picture.
SharePoint mark the column index enabled, and then add records with item identifier and index field id and value to sql table NameValuePair_[loc].
Related
I have been asked to review a series of indexes before they get added to our 2019 SQL db. I am not an index person and do not normally do this so I am trying to understand why I should add the one below.
The code below is adding two columns to a non-clustered index, when those two columns are always null. Essentially, I have a Part Master table that has 3 "sub category" fields. We only use 1 of those subcategory fields and never plan on using the others, so part_subgrp1 is populated while part_subgrp2 & 3 are always null. My peer keeps saying it will improve performance but they cannot explain why and I can't seem to get past how two blank fields help optimize search (at least in a meaningful way).
Here is the code:
5. new index from table partmstr
CREATE NONCLUSTERED INDEX [idx_partmstr_sellable_inclPartSubgrp2] ON [dbo].[partmstr]
(
[sellable], [part_grp]
)
include ([part_subgrp2],[part_subgrp3] )
GO
I don't know that it matters for the question but the table has 343 columns and 7704 records (and confirmed those two part sub groups are null for every one of those).
If he is correct I just want a better understanding of why so I don't feel like I am just putting junk in.
Thank you!
I am new, so if I jacked this up I will totally correct it. Thanks!
Can someone help me get into the thinking of knowing how to fix data in SQL tables (by trying NOT to give me an SQL routines I could run).
Ok, this is the situation…. Suppose I have a single table with has a column called ColumnA which has lots of duplicate values. I need to remove all the duplicate entries from the table in question. Question is….if I had to write pseudo-code as a plan, what SQL should be written
Many thanks to anyone who can offer me any pointers.
Kind Regards
James
I think you've already articulated a very basic psuedocode for the issue you describe in stating that you wish to delete duplicate values from column A.
For this example, I would tend to;
Find all instances of duplicates
Work out method of determining which one to keep (Google "MAX N in
Group" for ideas) There are good articles here on SO and DBA
Stackexchange also other external articles with examples
Write your delete to cater for the records you identify as unwanted
duplicates in the previous step
For me, when working through these types of issues in SQL Server, I tend to write a series of Common Table Expressions (CTE) to identify my target records and then delete based on that.
For example;
;WITH Duplicates AS (
-- Write your select query to identify which subset of your records are affected by having duplicate values in Column A
), TargetRows AS (
-- Further select from Duplicates some method of MAX N in Group to identify which of the rows are unwanted
) -- Then here DELETE from your table based upon your findings from above
I have a SQL server database, with about 40 tables that need to be searched. I just started looking into Lucene for .net. These tables that need to be searched doesn't have any column that identifies when the row was last updated or created. We don't want to change the table structure right now. What are the options I have to identify if a row in a table has modified so that I can update the document in the Lucene index? And same for newly created rows too. Any help is greatly appreciated.
If you can't tell what has changed by looking at the database, then just assume all of the rows have changed and update them all in Lucene. That handles your new rows as well.
If this is too slow or time consuming, then that gives you a reason why you should change your table structure to store the last updated date.
Two entries on my Django postgresql database are causing me a world of trouble when I go a-querying to create reports. When I try to delete these entries (via phpPgAdmin), I get the error "No unique identifier for this row." There are no duplicate IDs. I've tried updating all the fields. I've tried getting rid of these using the delete button and manual SQL commands. I'm out of ideas. Anyone know hot to give a row a unique identifier so I can get rid of it?
Thanks!
Look up the row by the special ctid system column and then delete by that value. ctid's are unique.
The rows you are going to delete may be referenced in another table.
remove them or refer them to something else and, then try to remove your given rows.
Wow, I'm having a bit of a headache with Access 2007. I have two tables, main_table and ref_table. when I store an int id in main_table corresponding to some record in ref_table, I get the looked up value of the record that I'm storing and not the int id. This isn't what I expected and I'd like access to behave like every other database on the face of the planet and show me the information how I stored it and not how it thinks I want to see it. Anyone know how to turn this 'feature' off?
Got it.
1-Go to design view of your table.
2-select the look-up tab bellow the field list.
3-Change row source type to "values".