Upgrade Rails on Mac

First let’s check our version:


ruby -v
rails -v
gem -v


In my case the Rails version was outdated. Let’s upgrade it:


sudo gem update --system
sudo gem update rails --include-dependencies
sudo gem update rake --include-dependencies
sudo gem update sqlite3-ruby --include-dependencies
sudo gem install mongrel # ok, this one is optional, but still nice to have, when switching from rails 1 to rails 2


sed one-liners

… more sed one-liners:

http://student.northpark.edu/pemente/sed/sed1line.txt

Multiline processing in sed

You want sed to replace backslash-newline to space (i.e. to convert multiline string into a singleline) like this:


param =
     val1, \
     val2, \
     val3


should become


param = val1, val2, val3


The following sed command does the trick

sed -e :a -e '/\\$/N; s/\\\n/ /; ta'

SQL Server 2005: XQuery snippets

Suppose we have an XML snippet:

<root>
  <tag1>val1</tag1>
  <tag2>val2</tag2>
</root>

1. To get all pairs
tag1 => val1
tag2 => val2
etc.

DECLARE @x XML;
SET @x = '<root><tag1>...</root>';
SELECT
  CAST(C.query('local-name(.)') AS NVARCHAR(4000)) AS [Tag],
  CAST(C.value('.', 'nvarchar(4000)') AS NVARCHAR(4000)) AS [Val]
FROM @x.nodes('/root/*') T(C);

2. To insert a new pair where value is to be taken from a local variable:

DECLARE @val NVARCHAR(4000);
SET @val = 'val0';
SET @x.modify('insert <tag0>{sql:variable("@val")}</tag0> as first into(/root)[1]');

Note how sql:variable() function was taken into curly braces, otherwise it would have inserted ‘sql:variable(“@val”)’. Also the modify() argument must be a string literal, i.e. the following construction does not work: ‘insert ‘ + @val + ‘ as first into(/root)[1]‘

3. To update a value:

DECLARE @val NVARCHAR(4000);
SET @val = 'val000';
SET @x.modify('replace value of (/root/tag0/text())[1] with sql:variable("@val")');

No curly braces but still have to use sql:variable() function.

Syntax Sugar in SQL Server 2005

1. Using OUTPUT clause:

DECLARE @NewKeys TABLE (
  [Key1]    UNIQUEIDENTIFIER NOT NULL,
  [Key2]    UNIQUEIDENTIFIER NOT NULL
);

UPDATE [XTable]
SET [Key2] = NEWID()
  OUTPUT inserted.[Key1], inserted.[Key2]
  INTO @NewKeys
WHERE [Key2] IS NULL;

Only updated rows go to @NewKeys table, of course a temporary or even a regular table can be used instead of table variable. No need for triggers.

2. Using JOIN with UPDATE:

UPDATE [x]
SET [x].[Key1] = [y].[Key1]
FROM [XTable] AS [x] INNER JOIN [YTable] AS [y]
ON [x].[Key2] = [y].[Key2]

SQL Server Management Studio: Vertical Split

You can split a SQL Server Management Studio horizontally. Nice feature I didn’t know about.

Open at least two tabs and go to Window -> New Vertical Tab Group

First post

In this blog I will post various tips, tricks, hack that I found helpful. This is just a reminder for myself.