SQL Server: temporary tables and constraint names

| category: Programming | author: st

Update. Since the version 2016 SQL Server supports anonymous constraint declaration:

CREATE TABLE #temp_table (
   id1 int NOT NULL,
   id2 int NOT NULL,
   name1 nvarchar(100),
   name2 nvarchar(100),
   PRIMARY KEY (id1, id2),
   UNIQUE (name1, name2)

For earlier versions the solution is below.

Local temporary tables are isolated in the scope …

C/C++: how to clear a linked circular list

| category: Programming | author: st
Tags: ,

In the case of linked circular list you need to add some checks to avoid memory corruption.

Full example (compiled OK with GCC 8.x)

#include <iostream>
#include <cstdlib>

struct Node
    Node(Node* prev, int val)
        : prev(prev), next(NULL), value(val)
    { }
    Node *prev, *next;
    int value;

void clear_list(Node …

SQL Server: key-value store table and hash index

| category: Testing | author: st
Tags: ,

Hash indexes are used as entry points for memory-optimized tables; both features were introduced in SQL Server 2014. Let's look at index performance in scenario "key-value store".

Scenario and environment

The table stores a significant volume (about 10 millions rows) of pairs key-value. The key is of integer type and …

SQL Server: fractional part of number

| category: Programming | author: st

Unfortunately, SQL Server doesn't have a function like frac to extract the fractional part of number. The method is to subtract the integer part from the origin value.

DECLARE @n1 float, @n2 float, @n3 float;
SELECT @n1 = 123.456, @n2 = 234.567, @n3 = 456.789;
SELECT @n1 - round(@n1, 0 …

SQL: generate random character string

| category: Programming | author: st

Collection of methods to generate random string in a single SQL statement

M1: Recursive string concatenation

On SQL Server the method is limited by 100 characters because of CTE recursion level limitation. The method has the performance issues when using in loops/joins because the table always have 100 rows …

SQL Server: sync two tables with MERGE statement

| category: Programming | author: st
Tags: ,

This small example shows how to synchronize the data of two tables using the MERGE statement

CREATE TABLE table1 (id int NOT NULL PRIMARY KEY, str_value nvarchar(50));
CREATE TABLE table2 (id int NOT NULL PRIMARY KEY, str_value nvarchar(50));
INSERT INTO table1 (id, str_value) VALUES (1, 'Value 1 …

Count LOC with Notepad++

| category: Programming | author: st

Notepad++ can count LOC (lines of code) of source files and give you the estimation of code size.

Press Ctrl+Shift+F shortcut to start "Find in files" dialog. Select "regular expression" search mode and start it.

Notepad++ LOC count

Some regular expressions:

  • \S+\s*$ -- all non-empty lines
  • ^\s*$ -- only empty (white-space) lines …

Classic backgroud color in Windows 10

| category: My notes | author: st

How to set classic background color in Windows 10?

  • Right click on desktop and select "Personalize" menu
  • Set "Background" option to "Solid color"
  • Click on "+ custom color" button
  • Click on "More"
  • Check that "RGB" is set
  • Enter "#336EA5" and click "Done" button

That's all.