L’integrazione tra .NET e SQL Server è data per scontata: in questo articolo esploreremo invece  come accedere a SQL Server da Python. Uno dei vantaggi di python è che è un linguaggio molto facile da imparare, con un notevole numero di librerie e un’ottima integrazione multi piattaforma. Oltre a ciò python offre un sistema di installazione rapido delle librerie (come  Ruby e Perl).

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At Gioorgi.com we was never a SQL fan. In 2000 we thinked SQL was boring, mostly because sql algebra could be a bit boring. Then we found this book written by one of the father of SQL. Years ago Google and then Facebook popped out with new incredible ideas, for improved and super fast scalability, which eventually turned to the “NoSQL” mantra.

But NoSQL is a mature technology, or it is only a path traced by the Social company out of there? Let’s explore together…

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 Dapper is a single file you can drop in to your project that will extend your IDbConnection interface. [...]

A key feature of Dapper is performance. The following metrics show how long it takes to execute 500 SELECT statements against a DB and map the data returned to objects.

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 Come evitare iniezione SQL: lato SQL Server (SP_EXECUTESQL)

In generale va evitato nel modo più assoluto la scrittura di query sql diamiche.

Va evitato cioè  l’uso lato SQL Server di sp_executesql e EXEC

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I stumbled upon a very brain-f**k error on Oracle 10g on these days.

Context: the following query [sql]SELECT * FROM (
SELECT TO_NUMBER(CUSTOMER_ID) AS SNDG FROM BAD_CODES_TABLE WHERE
AND I_LIKE=UPPER(‘STATIC_CONDITION’) AND CUSTOMER_ID NOT LIKE ‘%P%’ ) S WHERE TO_NUMBER(S.SNDG) >2000[/sql] could trigger a Invalid number if CUSTOMER_ID column contains invalid numbers.

Why?

Well…if you ask to “explain plan”, you will get something like

• a table full scan
  • Filter Predicates AND
    • I_LIKE=UPPER('STATIC_CONDITION')
    • TO_NUMBER(S.SNDG) >2000
    • CUSTOMER_ID NOT LIKE '%P%'

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[caption id=“attachment_5294” align=“alignright” width=“150”] Disapprove with me![/caption]

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On some environment, on some customers, Oracle connections are drop after some idle time (i.e. 2 minutes).

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Sometimes you need to remove nasty duplicate on a table, based on a subset of the column. On every big database there is something called “rowid” which can be used to indentify a column in a unique way. On PostgreSQL is called ctid, as we shall see:

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The Sqlite Oracle Compatibility Functions is an experimental compatibility layer for SQLite vs Oracle, written in Python 3.

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For a complete description see https://www.codeproject.com/Articles/33052/Visual-Representation-of-SQL-Joins