Tutorial by Examples: l

@Entity class Note { @Id Integer id; @Basic String note; @Transient String parsedNote; String readParsedNote() { if (parsedNote == null) { /* initialize from note */ } return parsedNote; } } If your class needs fields that should ...

Suppose we want to get all product categories with total sales greater than 20. Here is a query without Common Table Expressions: SELECT category.description, sum(product.price) as total_sales FROM sale LEFT JOIN product on sale.product_id = product.id LEFT JOIN category on product.category_id ...

Suppose we want to query the "cheapest products" from the "top categories". Here is an example of query using Common Table Expressions -- all_sales: just a simple SELECT with all the needed JOINS WITH all_sales AS ( SELECT product.price as product_price, category.id a...

SELECT x, ... FROM ( SELECT y, ... FROM ... ) AS a JOIN tbl ON tbl.x = a.y WHERE ... This will evaluate the subquery into a temp table, then JOIN that to tbl. Prior to 5.6, there could not be an index on the temp table. So, this was potentially very inefficient: SELECT ... ...

For...Next Using the iterator variable as the index number is the fastest way to iterate the elements of an array: Dim items As Variant items = Array(0, 1, 2, 3) Dim index As Integer For index = LBound(items) To UBound(items) 'assumes value can be implicitly converted to a String: D...

Skip lists are linked lists that allow you to skip to the correct node. This is a method which is way more fast than a normal singly linked list. It is basically a singly linked list but the pointers not going from one node to the next node, but skipping few nodes. Thus the name "Skip List&quo...

Partial method consists of the definition in one partial class declaration (as a common scenario - in the auto-generated one) and the implementation in another partial class declaration. using System; namespace PartialClassAndMethods { public partial class PartialClass // Auto-generated ...

TRUNCATE tableName; This will delete all the data and reset AUTO_INCREMENT index. It's much faster than DELETE FROM tableName on a huge dataset. It can be very useful during development/testing. When you truncate a table SQL server doesn't delete the data, it drops the table and recreates it, th...

Blocks are chunks of code enclosed between braces {} (usually for single-line blocks) or do..end (used for multi-line blocks). 5.times { puts "Hello world" } # recommended style for single line blocks 5.times do print "Hello " puts "world" end # recomme...

Objective c: //this is the dictionary you start with. NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:@"name1", @"Sam",@"name2", @"Sanju",nil]; //check if the dictionary contains the key you are going to modify. In this example, @&qu...

The following will echo each line in the file C:\scripts\testFile.txt. Blank lines will not be processed. for /F "tokens=*" %%A in (C:\scripts\testFile.txt) do ( echo %%A rem do other stuff here ) More advanced example shows, how derived in FOR loop from a restricted files set...

From command line: cpan -l From a Perl script: use ExtUtils::Installed; my $inst = ExtUtils::Installed->new(); my @modules = $inst->modules();

wildcard characters are used with the SQL LIKE operator. SQL wildcards are used to search for data within a table. Wildcards in SQL are:%, _, [charlist], [^charlist] % - A substitute for zero or more characters Eg: //selects all customers with a City starting with "Lo" SEL...

Simple one-liners may be specified as command line arguments to perl using the -e switch (think "execute"): perl -e'print "Hello, World!\n"' Due to Windows quoting rules you can't use single-quoted strings but have to use one of these variants: perl -e"print qq(Hello, W...

Windows uses only double quotes to wrap command line parameters. In order to use double quotes in perl one-liner (i.e. to print a string with an interpolated variable), you have to escape them with backslashes: perl -e "my $greeting = 'Hello'; print \"$greeting, world!\n\"" T...

perl -ne'print if /foo/' file.txt Case-insensitive: perl -ne'print if /foo/i' file.txt

perl -pe"s/foo/bar/g" file.txt Or in-place: perl -i -pe's/foo/bar/g' file.txt On Windows: perl -i.bak -pe"s/foo/bar/g" file.txt

perl -lane'print "$F[0] $F[-1]"' data.txt # prints the first and the last fields of a space delimited record CSV example: perl -F, -lane'print "$F[0] $F[-1]"' data.csv

perl -ne'print if 5..10' file.txt

Without a backup copy (not supported on Windows) perl -i -pe's/foo/bar/g' file.txt With a backup copy file.txt.bak perl -i.bak -pe's/foo/bar/g' file.txt With a backup copy old_file.txt.orig in the backup subdirectory (provided the latter exists): perl -i'backup/old_*.orig' -pe's/foo/bar/g' ...