SQL Server: Come fare ricerche CASE SENSITIVE

Carissimi lettori, ben torrnati!


L'articolo di ieri è stato sicuramente intenso (Database corrotti, recupero tramite DBCC WRITEPAGES) per cui oggi sarò molto più breve. Promesso!

Vi farò vedere come eseguire una ricerca case sentitive anche se la collate impostata sul database non lo è.


Ricerche case sensitive

Supponiamo di aver impostato sul nostro database una collate che non è case sensitive. Ovvero non è sensibile alle maiuscole e minuscole.

Supponiamo ora di avere una tabella "elenco" dentro la quale sono memorizzati una serie di nomi, come questa sotto:


SQL SSMS Query result

Ora, il nostro database non è case sensitive per cui una interrogazione come questa: 


SELECT * FROM ELENCO WHERE CODICE = 'LUCA'

ritornerà sempre entrambi i record.

Ma se volessimo restituito solamente il codice dove LUCA è scritto solo in minuscolo?
Come fare?

Bhe, il trucco è semplice.

Avete presente quando abbiamo parlato nei giorni scorsi di COLLATE?  (fai click qui:Errore Messaggio 468: Non è possibile risolvere il conflitto tra le regole di confronto "AAAA" e "BBBB" nell'operazione equal to. )

Avevamo accennato al fatto che è la COLLATE a stabilire se la nostra colonna è CASE SENSITIVE oppure no.

Ecco il trucco è proprio questo:  

Nella WHERE che andremo a scrivere andremo a specificare una COLLATE che sia CASE SENSITIVE.

Scriviamo ad esempio: 


SELECT * FROM ELENCO WHERE CODICE COLLATE SQL_Latin1_General_CP1_CS_AS = 'luca'

Eseguitela ed ecco il risultato..


 

 

 

Per oggi è tutto, ci vediamo presto..
P.S. Buon ferragosto! 


Luca Biondi @ SQLServerPerformance blog!

 
 
 
 
 
 
 
 
 

Comments

Post a Comment

I Post più popolari

Speaking to Sql Server, sniffing the TDS protocol

Image
Hello friends!  If yesterday you read my post and found it definitely boring (for the topic of course and not for how it was written to the author 😁) well today I promise you that the topic will be much more interesting! Let's talk about Sniffing , let's talk about going to see what happens when we "log in" or when we send a Query to SQL Server.  We will do this by taking a look to the little known tabular data stream (TDS) protocol built on top of the TCP/IP protocol. Ready! The TDS protocol What is the Tabular data stream (TDS) protocol?  The TDS is the protocol used by the SQL Server client Net-Library to communicates with SQL Server . TDS is specific to SQL Server and it is a low-level protocol that specifies both commands and data in a specific arrangement.  TDS encapsulate the TCP/IP protocol. Sniffing TDS packets you can read from the network the requests that your application do to the SQL Server and read the answer .   How to Sniff data from the ne...
Read more

SQL Server, find text in a Trigger, Stored Procedures, View and Function. Two ways and what ways is better

Image
Hi guys, Welcome back! Today a light post about a question that has been asked to me several times. The question is: how to  search for text inside a trigger or a stored procedure ? We have two different ways. A first way using a system view called syscomments: SELECT obj.xtype, text , * FROM sysobjects obj JOIN syscomments com on obj.id = com.id WHERE TEXT like '%text_that_i_am_searching_for%' A second way using a system view called sql_module: SELECT o. name AS Object_Name, o. type_desc , m. definition FROM sys.sql_modules m JOIN sys.objects o ON m. object_id = o. object_id WHERE m. definition Like '%text_that_i_am_searching_for%' ;   Another question is? What differences do we have in using one way instead of the other? Which solution is better? You have to consider that the system view sys.syscomment is obsolete and will be removed sooner or later. So don't use it in production enviroiments. The sys.sql_m...
Read more

SQL Server, Avoid that damn Table Spool!

Image
Hi guys, Welcome back for another post! A light one inspired from what i do during my work: many times I optimize queries rewriting them or adding index and i like it very much! Sometimes you need to use a little imagination, but everything you learn ... sooner or later it will come in handy! Enjoy the reading mates! Avoid the Table Spool, when you can A few days ago I came across a query whose execution time was very high ... or so it was for the client complaining about the problem. Before recreating it, let's create the structures and fill the tables with some data Create table PriceList (Id int identity (1,1) primary Key ,Code Varchar (20)) Insert into PriceList (code) select top 1000 right( '0000' + cast ( row_number () over ( order by id) as varchar (4)),4) from artico Insert into PriceList (code) select top 4000 right( '1000' + cast ( row_number () over ( order by id) as varchar (4)),4) from artico Create table OrdersList (Id int identity...
Read more