Category: Valentina SQL

[NEW] REGEX_REPLACE() function.

In 4.5.1 release we have add a new REGEX_REPLACE() function  to Valentina Expresions, which can be used in Table Methods, SQL and therefore, in Reports.

Up to now, we was able to do searches with the help of REGEX operator:

… WHERE fld REGEX ‘ab.[cdf]*’

New function brings the awesome power of REGEX to manipulate by strings stored in the database! Now we can not only search using REGEX, but modify strings! You can do that in the

  • SELECT EXPR, …
  • UPDATE TABLE T SET fld = EXPR

where EXPR is REGEX_REPLACE() function or contains it as a part.

Read details about this function here.

Internal optimization for views and sub-queries.

In some cases we can avoid copying sub-query result to the temporary table. We can even use sub-query cursor “as is” – so it could be used as a result of the whole query. In other words there  is almost zero overhead against a simple query.

For now such optimization can be applied if a query:

  1. contains only “*” item in the select list clause
  2. has no “where” clause
  3. has no “group by” clause
  4. has no “having” clause
  5. has no “distinct” clause
  6. is not a part of some join operation
  7. has no “order by” clause
  8. has no binding values
  9. sub-query is not a “union/except/intersect” result

Examples:

SELECT * FROM (SELECT * FROM t1 WHERE f1 > 5);

SELECT * FROM (SELECT t1.f1, t2 f1 FROM t1 JOIN t2 ON l1 WHERE t1.f1 > 5 AND t2.f1 <3);

Valentina SQL get powerful FORMAT() function.

Ivan have add into Valentina engine new very powerful FORMAT() function for SQL.

It provides great ability to convert numbers and date/times into string format.

Please read detailed syntax in the Valentina WIKI:
http://valentina-db.com/dokuwiki/doku.php?id=valentina:vcomponents:vsql:reference:expr:funcs_string#format

The same algorithms will be added in nearest time to Valentina Reports.

Improvements for stored procedures and binded queries

It was a huge improvement to solve the problem with a “second run” in stored procedures and binded queries.  Sometimes there was an incorrect behavior because of “over-prepared” nodes. There was a workaround with “EXECUTE” statement (which is actually developed  to prepare any SQL statement and execute one from another SQL statement). So now this workaround could be omitted.

Hierarchical (Recursive) Queries in Valentina SQL

There are three new kind of queries specially designed  for recursive (hierarchical) tables.

Such kind of tables are widely used. It could be human relationships, threaded forums and anything which might be described as tree-like data.

There are few common SQL ways to operate with such structures but all of them are too far from perfect.

Valentina introduces special kind of query which looks much more clear, natural and readable.

Syntax:
vext_recursive_table         -- v4.1
    :   {ANCESTORS | BROTHERS | DESCENDANTS} OF vext_root_objects
        [{TO|ON} LEVEL UINT] USING link_name [WITH {ROOT | ROOTS}]

vext_root_objects
    :   UINT
    |   variable_name
    |   ( search_condition )

Examples:

ANCESTORS OF (RecID IN(4,5)) ON LEVEL 1 USING l1
BROTHERS OF 4 ON LEVEL 2 USING l1
SELECT * FROM (ANCESTORS OF (RecID IN(4,5)) ON LEVEL 1 USING l1)  WHERE f1 = 'Branch2'

See also:

* WIKI: Valentina SQL Reference: Hierarchical (Recursive) Queries for description of exact syntax of these commands and examples.

* WIKI: Article Hierarchical (Recursive) Queries in Valentina SQL

Using of “Instead-of” triggers

Such kind of trigger may be applied to views only. It could be used for insert, update and delete operations as usual.

Example:

CREATE TRIGGER trigger1
INSTEAD OF INSERT ON v1
FOR EACH ROW
BEGIN
INSERT INTO t2 VALUES( 1 );
END ;

“trigger1” will be fired on attempt to insert record in the view “v1”.
Starting from v 4.1 you may use ‘NEW’ and ‘OLD’ descriptors within this kind of trigger.
Views are always read-only – so using the trigger is a nature way to overcome this restriction.

Example:

CREATE TABLE t1 (f1 LONG, f2 TEXT(1024));
CREATE VIEW v1 AS SELECT * FROM t1;
CREATE TRIGGER trigger1
INSTEAD OF INSERT ON v1
FOR EACH ROW
BEGIN
INSERT INTO t1 VALUES( NEW.f1, NEW.f2 );
END ;

—
INSERT INTO v1 VALUES ( 1, ‘abc’);

SELECT * FROM v1;
————-
f1 f2
————-
1 abc
————-

RAISE now can re-throw exception

Up to now the statement RAISE did have syntax as: 
     raise errNumber [, errMsg]

Now it is 
     raise [errNumber [, errMsg]]

Except syntax also is implemented additional logic:
     raise without parameters means throw the same exception forward.

BEGIN
INSERT INTO t1 VALUES(1);
INSERT INTO t1 VALUES(1);
EXCEPTION
WHEN 23503 THEN
PRINT 'Unique violation'
RAISE;
END;