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What does “fragment” mean in ANTLR?
...lly they'll improve readability of your grammars.
look at this example :
STRING : '"' (ESC | ~["\\])* '"' ;
fragment ESC : '\\' (["\\/bfnrt] | UNICODE) ;
fragment UNICODE : 'u' HEX HEX HEX HEX ;
fragment HEX : [0-9a-fA-F] ;
STRING is a lexer using fragment rule like ESC .Unicode is used in Esc r...
Equals(=) vs. LIKE
... these operators!
= is a comparison operator that operates on numbers and strings. When comparing strings, the comparison operator compares whole strings.
LIKE is a string operator that compares character by character.
To complicate matters, both operators use a collation which can have important...
Are there disadvantages to using a generic varchar(255) for all text-based fields?
... (If you're wondering, it's this way because Ruby on Rails migrations map String fields to VARCHAR(255) by default and I never bothered to override it).
...
What is the fastest/most efficient way to find the highest set bit (msb) in an integer in C?
... array.
NOTE: When using 64-bit values, be extremely cautious about using extra-clever algorithms; many of them only work correctly for 32-bit values.
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How to persist a property of type List in JPA?
... should anyone be looking for an alternative solution where you store your string lists as one field in your database, here's how I solved that. Create a Converter like this:
import java.util.Arrays;
import java.util.List;
import javax.persistence.AttributeConverter;
import javax.persistence.Conve...
Group query results by month and year in postgresql
...ht make sense to use date_trunc, but in some cases having a formatted date string is preferable, and if you're using a performant data warehouse the additional computation might not be a deal breaker. For example, if you are running a quick analytics report using redshift, and it usually takes 3 sec...
Can you explain the HttpURLConnection connection process?
...
String message = URLEncoder.encode("my message", "UTF-8");
try {
// instantiate the URL object with the target URL of the resource to
// request
URL url = new URL("http://www.example.com/comment");
// instan...
Resolve build errors due to circular dependency amongst classes
...o handle the forward declarations. The only "disadvantage" would be in the extra files. I assume you always include a.fwd.h in a.h, to assure they stay in sync. The example code is missing where these classes are used. a.h and b.h will both need to be included since they won't function in isolatio...
Please explain the exec() function and its family
... family have different behaviours:
l : arguments are passed as a list of strings to the main()
v : arguments are passed as an array of strings to the main()
p : path/s to search for the new running program
e : the environment can be specified by the caller
You can mix them, therefore you have:
...
How to change the CHARACTER SET (and COLLATION) throughout a database?
...DEFAULT is not null, CONCAT(' DEFAULT \'', COLUMN_DEFAULT, '\''), ''), if (EXTRA != '', CONCAT(' ', EXTRA), '')))), ';') as alter_statement
FROM information_schema.columns a
INNER JOIN INFORMATION_SCHEMA.TABLES b ON a.TABLE_CATALOG = b.TABLE_CATALOG
AND a.TABLE_SCHEMA = b.TABLE_SCHEM...