Karlee Will

Karlee Will

1645498873

You Should Crush These 5 Common SQL Issues

Having great skill in SQL is a an asset for any Data Scientist. Both learning new concepts and revising them thoroughly can be accomplished by picking and solving some common problems asked in the domain. In this article, I’m going to relay 5 such problems, that I’ve handpicked from LeetCode and describe what they want and lay down the approaches to solving them.

1. Combine Two Tables
2. Customers Who Never Order
3. Second Highest Salary
4. Duplicate Emails
5. Rising Temperature

#sql 

What is GEEK

Buddha Community

You Should Crush These 5 Common SQL Issues
Cayla Erdman

Cayla Erdman

1594369800

Introduction to Structured Query Language SQL pdf

SQL stands for Structured Query Language. SQL is a scripting language expected to store, control, and inquiry information put away in social databases. The main manifestation of SQL showed up in 1974, when a gathering in IBM built up the principal model of a social database. The primary business social database was discharged by Relational Software later turning out to be Oracle.

Models for SQL exist. In any case, the SQL that can be utilized on every last one of the major RDBMS today is in various flavors. This is because of two reasons:

1. The SQL order standard is genuinely intricate, and it isn’t handy to actualize the whole standard.

2. Every database seller needs an approach to separate its item from others.

Right now, contrasts are noted where fitting.

#programming books #beginning sql pdf #commands sql #download free sql full book pdf #introduction to sql pdf #introduction to sql ppt #introduction to sql #practical sql pdf #sql commands pdf with examples free download #sql commands #sql free bool download #sql guide #sql language #sql pdf #sql ppt #sql programming language #sql tutorial for beginners #sql tutorial pdf #sql #structured query language pdf #structured query language ppt #structured query language

Spring Framework

Spring Framework

1642110180

Spring: A Static Web Site Generator Written By GitHub Issues

Spring

Spring is a blog engine written by GitHub Issues, or is a simple, static web site generator. No more server and database, you can setup it in free hosting with GitHub Pages as a repository, then post the blogs in the repository Issues.

You can add some labels in your repository Issues as the blog category, and create Issues for writing blog content through Markdown.

Spring has responsive templates, looking good on mobile, tablet, and desktop.Gracefully degrading in older browsers. Compatible with Internet Explorer 10+ and all modern browsers.

Get up and running in seconds.

中文介绍

Quick start guide

For the impatient, here's how to get a Spring blog site up and running.

First of all

  • Fork the Spring repository as yours.
  • Goto your repository settings page to rename Repository Name.
  • Hosted directly on GitHub Pages from your project repository, you can take it as User or organization site or Project site(create a gh-pages branch).
  • Also, you can set up a custom domain with Pages.

Secondly

  • Open the index.html file to edit the config variables with yours below.
$.extend(spring.config, {
  // my blog title
  title: 'Spring',
  // my blog description
  desc: "A blog engine written by github issues [Fork me on GitHub](https://github.com/zhaoda/spring)",
  // my github username
  owner: 'zhaoda',
  // creator's username
  creator: 'zhaoda',
  // the repository name on github for writting issues
  repo: 'spring',
  // custom page
  pages: [
  ]
})
  • Put your domain into the CNAME file if you have.
  • Commit your change and push it.

And then

  • Goto your repository settings page to turn on the Issues feature.
  • Browser this repository's issues page, like this https://github.com/your-username/your-repo-name/issues?state=open.
  • Click the New Issue button to just write some content as a new one blog.

Finally

  • Browser this repository's GitHub Pages url, like this http://your-username.github.io/your-repo-name, you will see your Spring blog, have a test.
  • And you're done!

Custom development

Installation

  • You will need a web server installed on your system, for example, Nginx, Apache etc.
  • Configure your spring project to your local web server directory.
  • Run and browser it, like http://localhost/spring/dev.html .
  • dev.html is used to develop, index.html is used to runtime.

Folder Structure

spring/
├── css/
|    ├── boot.less  #import other less files
|    ├── github.less  #github highlight style
|    ├── home.less  #home page style
|    ├── issuelist.less #issue list widget style
|    ├── issues.less #issues page style
|    ├── labels.less #labels page style
|    ├── main.less #commo style
|    ├── markdown.less #markdown format style
|    ├── menu.less #menu panel style
|    ├── normalize.less #normalize style
|    ├── pull2refresh.less #pull2refresh widget style
|    └── side.html  #side panel style
├── dist/
|    ├── main.min.css  #css for runtime
|    └── main.min.js  #js for runtime
├── img/  #some icon, startup images
├── js/
|    ├── lib/  #some js librarys need to use
|    ├── boot.js  #boot
|    ├── home.js  #home page
|    ├── issuelist.js #issue list widget
|    ├── issues.js #issues page
|    ├── labels.js #labels page
|    ├── menu.js #menu panel
|    ├── pull2refresh.less #pull2refresh widget
|    └── side.html  #side panel
├── css/
|    ├── boot.less  #import other less files
|    ├── github.less  #github highlight style
|    ├── home.less  #home page style
|    ├── issuelist.less #issue list widget style
|    ├── issues.less #issues page style
|    ├── labels.less #labels page style
|    ├── main.less #commo style
|    ├── markdown.less #markdown format style
|    ├── menu.less #menu panel style
|    ├── normalize.less #normalize style
|    ├── pull2refresh.less #pull2refresh widget style
|    └── side.html  #side panel style
├── dev.html #used to develop
├── favicon.ico #website icon
├── Gruntfile.js #Grunt task config
├── index.html #used to runtime
└── package.json  #nodejs install config

Customization

  • Browser http://localhost/spring/dev.html, enter the development mode.
  • Changes you want to modify the source code, like css, js etc.
  • Refresh dev.html view change.

Building

  • You will need Node.js installed on your system.
  • Installation package.
bash

$ npm install

*   Run grunt task.

    ```bash
$ grunt
  • Browser http://localhost/spring/index.html, enter the runtime mode.
  • If there is no problem, commit and push the code.
  • Don't forget to merge master branch into gh-pages branch if you have.
  • And you're done! Good luck!

Report a bug

Who used

If you are using, please tell me.

Download Details:
Author: zhaoda
Source Code: https://github.com/zhaoda/spring
License: MIT License

#spring #spring-framework #spring-boot #java 

Cayla Erdman

Cayla Erdman

1596441660

Welcome Back the T-SQL Debugger with SQL Complete – SQL Debugger

When you develop large chunks of T-SQL code with the help of the SQL Server Management Studio tool, it is essential to test the “Live” behavior of your code by making sure that each small piece of code works fine and being able to allocate any error message that may cause a failure within that code.

The easiest way to perform that would be to use the T-SQL debugger feature, which used to be built-in over the SQL Server Management Studio tool. But since the T-SQL debugger feature was removed completely from SQL Server Management Studio 18 and later editions, we need a replacement for that feature. This is because we cannot keep using the old versions of SSMS just to support the T-SQL Debugger feature without “enjoying” the new features and bug fixes that are released in the new SSMS versions.

If you plan to wait for SSMS to bring back the T-SQL Debugger feature, vote in the Put Debugger back into SSMS 18 to ask Microsoft to reintroduce it.

As for me, I searched for an alternative tool for a T-SQL Debugger SSMS built-in feature and found that Devart company rolled out a new T-SQL Debugger feature to version 6.4 of SQL – Complete tool. SQL Complete is an add-in for Visual Studio and SSMS that offers scripts autocompletion capabilities, which help develop and debug your SQL database project.

The SQL Debugger feature of SQL Complete allows you to check the execution of your scripts, procedures, functions, and triggers step by step by adding breakpoints to the lines where you plan to start, suspend, evaluate, step through, and then to continue the execution of your script.

You can download SQL Complete from the dbForge Download page and install it on your machine using a straight-forward installation wizard. The wizard will ask you to specify the installation path for the SQL Complete tool and the versions of SSMS and Visual Studio that you plan to install the SQL Complete on, as an add-in, from the versions that are installed on your machine, as shown below:

Once SQL Complete is fully installed on your machine, the dbForge SQL Complete installation wizard will notify you of whether the installation was completed successfully or the wizard faced any specific issue that you can troubleshoot and fix easily. If there are no issues, the wizard will provide you with an option to open the SSMS tool and start using the SQL Complete tool, as displayed below:

When you open SSMS, you will see a new “Debug” tools menu, under which you can navigate the SQL Debugger feature options. Besides, you will see a list of icons that will be used to control the debug mode of the T-SQL query at the leftmost side of the SSMS tool. If you cannot see the list, you can go to View -> Toolbars -> Debugger to make these icons visible.

During the debugging session, the SQL Debugger icons will be as follows:

The functionality of these icons within the SQL Debugger can be summarized as:

  • Adding Breakpoints to control the execution pause of the T-SQL script at a specific statement allows you to check the debugging information of the T-SQL statements such as the values for the parameters and the variables.
  • Step Into is “navigate” through the script statements one by one, allowing you to check how each statement behaves.
  • Step Over is “execute” a specific stored procedure if you are sure that it contains no error.
  • Step Out is “return” from the stored procedure, function, or trigger to the main debugging window.
  • Continue executing the script until reaching the next breakpoint.
  • Stop Debugging is “terminate” the debugging session.
  • Restart “stop and start” the current debugging session.

#sql server #sql #sql debugger #sql server #sql server stored procedure #ssms #t-sql queries

Cayla Erdman

Cayla Erdman

1596448980

The Easy Guide on How to Use Subqueries in SQL Server

Let’s say the chief credit and collections officer asks you to list down the names of people, their unpaid balances per month, and the current running balance and wants you to import this data array into Excel. The purpose is to analyze the data and come up with an offer making payments lighter to mitigate the effects of the COVID19 pandemic.

Do you opt to use a query and a nested subquery or a join? What decision will you make?

SQL Subqueries – What Are They?

Before we do a deep dive into syntax, performance impact, and caveats, why not define a subquery first?

In the simplest terms, a subquery is a query within a query. While a query that embodies a subquery is the outer query, we refer to a subquery as the inner query or inner select. And parentheses enclose a subquery similar to the structure below:

SELECT 
 col1
,col2
,(subquery) as col3
FROM table1
[JOIN table2 ON table1.col1 = table2.col2]
WHERE col1 <operator> (subquery)

We are going to look upon the following points in this post:

  • SQL subquery syntax depending on different subquery types and operators.
  • When and in what sort of statements one can use a subquery.
  • Performance implications vs. JOINs.
  • Common caveats when using SQL subqueries.

As is customary, we provide examples and illustrations to enhance understanding. But bear in mind that the main focus of this post is on subqueries in SQL Server.

Now, let’s get started.

Make SQL Subqueries That Are Self-Contained or Correlated

For one thing, subqueries are categorized based on their dependency on the outer query.

Let me describe what a self-contained subquery is.

Self-contained subqueries (or sometimes referred to as non-correlated or simple subqueries) are independent of the tables in the outer query. Let me illustrate this:

-- Get sales orders of customers from Southwest United States 
-- (TerritoryID = 4)

USE [AdventureWorks]
GO
SELECT CustomerID, SalesOrderID
FROM Sales.SalesOrderHeader
WHERE CustomerID IN (SELECT [CustomerID]
                     FROM [AdventureWorks].[Sales].[Customer]
                     WHERE TerritoryID = 4)

As demonstrated in the above code, the subquery (enclosed in parentheses below) has no references to any column in the outer query. Additionally, you can highlight the subquery in SQL Server Management Studio and execute it without getting any runtime errors.

Which, in turn, leads to easier debugging of self-contained subqueries.

The next thing to consider is correlated subqueries. Compared to its self-contained counterpart, this one has at least one column being referenced from the outer query. To clarify, I will provide an example:

USE [AdventureWorks]
GO
SELECT DISTINCT a.LastName, a.FirstName, b.BusinessEntityID
FROM Person.Person AS p
JOIN HumanResources.Employee AS e ON p.BusinessEntityID = e.BusinessEntityID
WHERE 1262000.00 IN
    (SELECT [SalesQuota]
    FROM Sales.SalesPersonQuotaHistory spq
    WHERE p.BusinessEntityID = spq.BusinessEntityID)

Were you attentive enough to notice the reference to BusinessEntityID from the Person table? Well done!

Once a column from the outer query is referenced in the subquery, it becomes a correlated subquery. One more point to consider: if you highlight a subquery and execute it, an error will occur.

And yes, you are absolutely right: this makes correlated subqueries pretty harder to debug.

To make debugging possible, follow these steps:

  • isolate the subquery.
  • replace the reference to the outer query with a constant value.

Isolating the subquery for debugging will make it look like this:

SELECT [SalesQuota]
    FROM Sales.SalesPersonQuotaHistory spq
    WHERE spq.BusinessEntityID = <constant value>

Now, let’s dig a little deeper into the output of subqueries.

Make SQL Subqueries With 3 Possible Returned Values

Well, first, let’s think of what returned values can we expect from SQL subqueries.

In fact, there are 3 possible outcomes:

  • A single value
  • Multiple values
  • Whole tables

Single Value

Let’s start with single-valued output. This type of subquery can appear anywhere in the outer query where an expression is expected, like the WHERE clause.

-- Output a single value which is the maximum or last TransactionID
USE [AdventureWorks]
GO
SELECT TransactionID, ProductID, TransactionDate, Quantity
FROM Production.TransactionHistory
WHERE TransactionID = (SELECT MAX(t.TransactionID) 
                       FROM Production.TransactionHistory t)

When you use a MAX() function, you retrieve a single value. That’s exactly what happened to our subquery above. Using the equal (=) operator tells SQL Server that you expect a single value. Another thing: if the subquery returns multiple values using the equals (=) operator, you get an error, similar to the one below:

Msg 512, Level 16, State 1, Line 20
Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression.

Multiple Values

Next, we examine the multi-valued output. This kind of subquery returns a list of values with a single column. Additionally, operators like IN and NOT IN will expect one or more values.

-- Output multiple values which is a list of customers with lastnames that --- start with 'I'

USE [AdventureWorks]
GO
SELECT [SalesOrderID], [OrderDate], [ShipDate], [CustomerID]
FROM Sales.SalesOrderHeader
WHERE [CustomerID] IN (SELECT c.[CustomerID] FROM Sales.Customer c
INNER JOIN Person.Person p ON c.PersonID = p.BusinessEntityID
WHERE p.lastname LIKE N'I%' AND p.PersonType='SC')

Whole Table Values

And last but not least, why not delve into whole table outputs.

-- Output a table of values based on sales orders
USE [AdventureWorks]
GO
SELECT [ShipYear],
COUNT(DISTINCT [CustomerID]) AS CustomerCount
FROM (SELECT YEAR([ShipDate]) AS [ShipYear], [CustomerID] 
      FROM Sales.SalesOrderHeader) AS Shipments
GROUP BY [ShipYear]
ORDER BY [ShipYear]

Have you noticed the FROM clause?

Instead of using a table, it used a subquery. This is called a derived table or a table subquery.

And now, let me present you some ground rules when using this sort of query:

  • All columns in the subquery should have unique names. Much like a physical table, a derived table should have unique column names.
  • ORDER BY is not allowed unless TOP is also specified. That’s because the derived table represents a relational table where rows have no defined order.

In this case, a derived table has the benefits of a physical table. That’s why in our example, we can use COUNT() in one of the columns of the derived table.

That’s about all regarding subquery outputs. But before we get any further, you may have noticed that the logic behind the example for multiple values and others as well can also be done using a JOIN.

-- Output multiple values which is a list of customers with lastnames that start with 'I'
USE [AdventureWorks]
GO
SELECT o.[SalesOrderID], o.[OrderDate], o.[ShipDate], o.[CustomerID]
FROM Sales.SalesOrderHeader o
INNER JOIN Sales.Customer c on o.CustomerID = c.CustomerID
INNER JOIN Person.Person p ON c.PersonID = p.BusinessEntityID
WHERE p.LastName LIKE N'I%' AND p.PersonType = 'SC'

In fact, the output will be the same. But which one performs better?

Before we get into that, let me tell you that I have dedicated a section to this hot topic. We’ll examine it with complete execution plans and have a look at illustrations.

So, bear with me for a moment. Let’s discuss another way to place your subqueries.

#sql server #sql query #sql server #sql subqueries #t-sql statements #sql

Ruth Nabimanya

Ruth Nabimanya

1621850444

List of Available Database for Current User In SQL Server

Introduction

When working in the SQL Server, we may have to check some other databases other than the current one which we are working. In that scenario we may not be sure that does we have access to those Databases?. In this article we discuss the list of databases that are available for the current logged user in SQL Server

Get the list of database
Conclusion

#sql server #available databases for current user #check database has access #list of available database #sql #sql query #sql server database #sql tips #sql tips and tricks #tips