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7. October 2012

SQLite: escaping table and column names correctly

Filed under: DBMS,PHP,phpLiteAdmin — Tags: , , , , , , , , , , — Christopher Kramer @ 21:44

Summary:

Use double quotes around column names, table names, trigger names etc.

SELECT "column name", "my column", FROM "table name"

Use single quotes around string values

SELECT * FROM "table name" WHERE "column name" = 'string value'

Use two double quotes if e.g. your column name contains a double quote (e.g. my”column)

SELECT "my""column" FROM "my""table"

Details:

I joined the development team of phpliteadmin some months ago and am currently fixing several issues. One problem is caused by SQLite’s flexibility of column- and table names. A column named “SELECT”, “my column”, “this, that”, or even “this contains ‘single quotes'” is completely legal in SQLite. And what is legal is being used. So phpliteadmin needs to be able to handle these types of names as well, which is not really the case at the moment.

Let’s assume you query a column called “select”, you are likely to get errors like that in PHP:

Warning: SQLiteDatabase::query() [sqlitedatabase.query]: near “select”: syntax error in …

Or using PDO:

HY000 / 1 / near “select”: syntax error

From MySQL I knew backticks around table or column identifiers like in this example:

SELECT `select`, `my column`, `this, that` FROM `group by table`

(By the way, you see my syntax highlighter has problems with reserved words as column names as well ;-))

I tried this in SQLite and it worked, so I went that way. But there are different versions of SQLite and for the old version that, in PHP, is implemented by SQLiteDatabase, would give the following error:

Warning: SQLiteDatabase::query() [sqlitedatabase.query]: unrecognized token: “`” in …

So I found out that instead of backticks, normal single quotes work:

SELECT * FROM 'group by table'

This works well, but there is a problem here with column names:

SELECT 'select' FROM 'group by table'

This will not work as expected. It will not return the values of the column ‘select’, but create a column filled with the text ‘select’. That is of course standard SQL behaviour and shows that it is a bad idea to use single quotes around column or table names. The bug report by maitredede on the phpliteadmin issue tracker made me aware of another way to escape column and table names:

SELECT [select], [my column], [this, that] FROM [group by table]

This works very well, both with SQLiteDatabase, SQLite3 and PDO when accessing SQLite from PHP. I have not tried it using the SQLite C library directly, but it should work as well.

So I’d say this is the best way to do this as it works the same way with all versions of SQLite / all PHP SQLite extensions.

 

Update:

Well, probably I should have read the manual first:

SQlite supports ` for compatibility with MySQL and [] for compatibility with MS Access and SQL Server. But it also supports double quotes, which is standard SQL. So I’d say this is the best way to do it:

SELECT "select", "my column", "this, that" FROM "group by table"

It works with all SQLite versions / extensions just like the [] syntax. (And my syntax highlighter supports it as well ;-).)

Update 2:

Another thing that might be of interest: What to do, if a column/table name contains double quotes? Well, in this case duplicate them and you are done. Let’s assume you have a column called like this:

my “column

Then you query it like this:

SELECT "my""column" FROM "my_table"

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30. May 2012

Released: phpLiteAdmin 1.9.2 includes CSV import/export

Filed under: DBMS,PHP,phpLiteAdmin,Server Administration — Tags: , , , , , , — Christopher Kramer @ 15:54

As I wrote in March, I implemented CSV import and fixed export issues of phpLiteAdmin. This fixed phpLiteAdmin bug #71. I also wrote a small fix for bug #75. Today, new version 1.9.2 of phpLiteAdmin was released including both fixes. You can download it here.

I’d like to thank the phpLiteAdmin team for including my work and allowing me to join the team. I plan to address more issues of phpLiteAdmin in the future to push phpLiteAdmin a little further. There is still some more work to be done which I will have a look at once I find the time.

I recommend the new version to anybody using phpLiteAdmin (and also everybody who doesn’t yet ;-)). Please use the bugtracker in case you find any issues.

I hope some of you find the new features useful or are happy to see those bugs fixed.

Thanks again to the phpLiteAdmin team for the great tool and the opportunity to contribute to the project. Fortunately, I do not have to create a fork to improve the tool.

 

10. March 2012

phpliteadmin: CSV import and export

Filed under: DBMS,PHP,phpLiteAdmin,Server Administration — Tags: , , , , , , , , — Christopher Kramer @ 12:24

In case you use sqlite, a serverless, transactional SQL-complete database engine, you might also know phpliteadmin. It is a web-based DB admin tool just like phpMyAdmin is for MySQL. It is small and does not require complex installation just like sqlite. It is great to do most simple operations on a sqlite database, but in my opinion it still has some important limitations and bugs.

One thing I recently missed was the possibility to import CSV files into a SQLite database. The SQLite shell makes this very easy (if the file has the correct syntax). But this has also some limitations and you have to leave the phpLiteAdmin GUI and start a SQLite shell. So I thought it should be part of phpLiteAdmin. It already had some GUI options for CSV import, but the actual import implementation was missing, so I implemented CSV import myself. On the way testing the exported csv and importing it again I noticed some export bugs of phpliteadmin like this one and fixed them on the way.

So those are the changes I did to phpLiteAdmin:

Import:

  • implemented CSV import with some features like:
  • you can define Enclosure, Escaper, Null and first-row-field-description just like when exporting
  • using PHP’s fgetcsv()
  • can import files that were exported with phpliteadmin using the same settings!
  • can even import files exported with phpliteadmin without my corrections and improvements (see below), although they are not “standard CSV”.

Export:

  • removed line terminator option because:
    • this was not implemented
    • in my opinion anything else than a linebreak does not make sense, so useless feature
  • Fix: Tables with indexes were exported multiple times
  • Fix: Last column was terminated which is not usual in CSV
  • NULLs are not enclosed anymore to allow distinction between “NULL”-text
  • FIX: Removing CRLF was not implemented
  • FIX: Tables that were not exported caused additional linebreaks in output

You can find anything related to these changes in phpLiteAdmin’s bug tracker.

You can also get my version with the improvements from the bugtracker or download it here.

I really hope this will make it into the next release of phpLiteAdmin, but unfortunately I did not get any feedback by the developers of phpLiteAdmin yet. Hopefully this is not getting a fork 😉

I hope you like these features and bugfixes. You can give me feedback here or in the phpliteadmin bug tracker.

I really think a good database management tool for SQLite is needed and phpLiteAdmin has the potential to become one. We will see.

You can also tell me if you use some other management tool for SQLite which you think is way better 😉

Update 2012/05/13: The phpliteadmin developers just announced that an official new version including these improvements will come up soon. Great news, I am looking forward to this new version!

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