How to install PostgreSQL on Mac using Homebrew

Click the link: "How to install PostgreSQL on Mac using Homebrew"

In this tutorial we will learn to install PostgreSQL database on Mac using Homebrew.

Prerequisite

It is assumed that you have Homebrew installed on your Mac.

If you don't have Homebrew installed on your Mac then open Terminal and run the following command.

$ /usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"

Alright, time to install PostgreSQL on Mac.

Install PostgreSQL using Homebrew

In Terminal run the following command to install PostgreSQL on Mac using Homebrew.

$ brew install postgres

Start PostgreSQL

To start PostgreSQL run the following command in the Terminal.

$ brew services start postgres

Stop PostgreSQL

To stop PostgreSQL run the following command in the Terminal.

$ brew services stop postgres

Restart PostgreSQL

To restart PostgreSQL run the following command in the Terminal.

$ brew services restart postgres

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How to change default shell to bash on macOS Catalina

Click the link: "How to change default shell to bash on macOS Catalina"

In this tutorial we will learn to change default shell to bash on macOS Catalina 10.15.

With the release of macOS Catalina 10.15 on 7th October 2019 Apple made zsh as the default shell. You can learn more about it here.

From Apple:

By default, your Mac uses either zsh or bash as the command-line interpreter for the login shell and interactive shell:

• zsh (Z shell) is the default shell for all newly created user accounts, starting with the macOS Catalina beta.
• bash is the default shell in macOS Mojave and earlier.

If you want to make bash as your default command-line interpreter then perform the following steps.

Close Terminal if it is open.

Step 1: Open System Preferences and select Users & Groups

Click on the System Preferences icon or hit Cmd + Spacebar to open Spotlight and type System Preferences and open it.

Now, select Users & Groups.

Step 2: Unlock

At the bottom left you will see the lock. Click it and enter your password to unlock it.

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How to install Apache, MySQL, PHP on macOS Catalina 10.15

Click the link: "How to install Apache, MySQL, PHP on macOS Catalina 10.15"

In this tutorial we will learn to install Apache, MySQL, PHP on macOS Catalina 10.15.

About macOS Catalina

Apple released macOS Catalina 10.15 on 7th October 2019 and it includes Apache and PHP. So, all we have to do is enable them. Then install MySQL and we are ready for development. So, lets get started.

Note! Support for 32 bit apps is removed in Catalina so, all your 32 bit applications will no longer work. Kindly upgrade your applications.

Apple has also made zsh as the default shell. You can learn more about it here.

To change the default shell check the tutorial How to change default shell to bash on macOS Catalina.

We will be using the pre-installed Apache and PHP and we will download and setup MySQL database.

If you are using macOS Mojave then check out this tutorial How to install Apache, MySQL, PHP on macOS Mojave 10.14

Let's go ahead and configure our LAMP stack development environment on macOS Catalina.

Apache

The new macOS Catalina comes with Apache pre-installed. All we have to do is switch it on.

Open Terminal using macOS Spotlight or go to /Applications/Utilities and open Terminal.

To check the version of Apache installed run the following command in the Terminal.

$ httpd -v

Server version: Apache/2.4.41 (Unix)
Server built:   Aug 29 2019 19:01:57

Note! macOS Catalina comes with Apache 2.4.41

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MongoDB - Delete Documents

Click the link: "MongoDB - Delete Documents"

In this MongoDB tutorial we will learn to delete documents.

Login to your MongoDB server and insert the following documents.

For this tutorial I will insert the documents in the subscription collection.

> db.subscription.insertMany([
  {
    "firstname": "John",
    "lastname": "Doe",
    "uid": 1,
    "accountstatus": "ACTIVE",
    "plan": "TRIAL15DAYS",
    "modifiedAt": null,
    "createdAt": new Date()
  },
  {
    "firstname": "Jane",
    "lastname": "Doe",
    "uid": 2,
    "accountstatus": "ACTIVE",
    "plan": "PLAN30DAYS",
    "modifiedAt": null,
    "createdAt": new Date()
  },
  {
    "firstname": "Jim",
    "lastname": "Doe",
    "uid": 3,
    "accountstatus": "SUSPENDED",
    "plan": "PLAN60DAYS",
    "modifiedAt": null,
    "createdAt": new Date()
  },
  {
    "firstname": "Alice",
    "lastname": "Doe",
    "uid": 4,
    "accountstatus": "ACTIVE",
    "plan": "PLAN1YEAR",
    "modifiedAt": null,
    "createdAt": new Date()
  }
])

Note! We are using new Date() to set the createdAt to current date time.

Delete one document

We use the deleteOne method to delete one document from a given collection.

In the following example we are deleting document having uid equal to 4.

> db.subscription.deleteOne({ "uid": 4 })

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MongoDB - Update Documents

Click the link: "MongoDB - Update Documents"

In this MongoDB tutorial we will learn to update documents.

Login to your MongoDB server and insert the following documents.

For this tutorial I will insert the documents in the subscription collection.

> db.subscription.insertMany([
  {
    "firstname": "John",
    "lastname": "Doe",
    "uid": 1,
    "accountstatus": "ACTIVE",
    "plan": "TRIAL15DAYS",
    "modifiedAt": null,
    "createdAt": new Date()
  },
  {
    "firstname": "Jane",
    "lastname": "Doe",
    "uid": 2,
    "accountstatus": "ACTIVE",
    "plan": "PLAN30DAYS",
    "modifiedAt": null,
    "createdAt": new Date()
  },
  {
    "firstname": "Jim",
    "lastname": "Doe",
    "uid": 3,
    "accountstatus": "SUSPENDED",
    "plan": "PLAN60DAYS",
    "modifiedAt": null,
    "createdAt": new Date()
  },
  {
    "firstname": "Alice",
    "lastname": "Doe",
    "uid": 4,
    "accountstatus": "ACTIVE",
    "plan": "PLAN1YEAR",
    "modifiedAt": null,
    "createdAt": new Date()
  }
])

Note! We are using new Date() to set the createdAt to current date time.

Update one document

To update a single document we use updateOne method.

Syntax

db.collectionName.updateOne(filter, update)

Where, filter is the condition to get the required document and update is the part of the document we want to update.

In the following example we are updating the account status of user having uid equal to 3 from SUSPENDED to ACTIVE.

> db.subscription.updateOne(
  { "uid": 3 },
  {
    $set: { "accountstatus": "ACTIVE" },
    $currentDate: { "modifiedAt": true }
  }
)

We use $set operator to update the value of accountstatus.

We use $currentDate operator to set the modifiedAt to current date.

If we now fetch the above document we will get the following.

> db.subscription.find({ "uid": 3 }).pretty()

{
  "_id" : ObjectId("5d7715d5b385796f53d4c8ff"),
  "firstname" : "Jim",
  "lastname" : "Doe",
  "uid" : 3,
  "accountstatus" : "ACTIVE",
  "plan" : "PLAN60DAYS",
  "modifiedAt" : ISODate("2019-09-10T03:18:42.406Z"),
  "createdAt" : ISODate("2019-09-10T03:17:41.130Z")
}

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MongoDB - Query for Null and Missing fields

Click the link: "MongoDB - Query for Null and Missing fields"

In this MongoDB tutorial we will learn to query for Null and missing fields.

Login to your MongoDB server and insert the following documents.

For this tutorial I will insert the documents in the deliveryAddress collection.

> db.deliveryAddress.insertMany([
  {
    "addressLine1": "House #1, 2nd Street, 1st Main Road",
    "addressLine2": "Opposite Bakery",
    "city": "Bangalore",
    "state": "KA",
    "country": "India",
    "pincode": "560001",
    "contactphone": "919800000000",
    "contactperson": "John Doe"
  },
  {
    "addressLine1": "House #20, 3rd Street, 5th Main Road",
    "addressLine2": null,
    "city": "Bangalore",
    "state": "KA",
    "country": "India",
    "pincode": "560001",
    "contactperson": "Jane Doe"
  },
  {
    "addressLine1": "House #20, 5th Street, 10th Main Road",
    "addressLine2": null,
    "city": "Bangalore",
    "state": "KA",
    "country": "India",
    "pincode": "560001",
    "contactphone": null,
    "contactperson": "Jim Doe"
  }
])

Select all documents having null field

In the following example we are fetching all the documents that have addressLine2 field set to null value.

> db.deliveryAddress.find({ "addressLine2": null }).pretty()


{
  "_id" : ObjectId("5d76170f89ccf6fae0c7974b"),
  "addressLine1" : "House #20, 3rd Street, 5th Main Road",
  "addressLine2" : null,
  "city" : "Bangalore",
  "state" : "KA",
  "country" : "India",
  "pincode" : "560001",
  "contactperson" : "Jane Doe"
}
{
  "_id" : ObjectId("5d76170f89ccf6fae0c7974c"),
  "addressLine1" : "House #20, 5th Street, 10th Main Road",
  "addressLine2" : null,
  "city" : "Bangalore",
  "state" : "KA",
  "country" : "India",
  "pincode" : "560001",
  "contactphone" : null,
  "contactperson" : "Jim Doe"
}

The $exists operator

To check if a document does or does not contains a given field we use the $exists operator.

Syntax

We use the following syntax to fetch all the documents of a given collection that does contains a given field.

db.collectionName.find({ field: { $exists: true } })

We use the following syntax to fetch all the documents of a given collection that does not contains a given field.

db.collectionName.find({ field: { $exists: false } })

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MongoDB - Query an Array of Embedded Documents

Click the link: "MongoDB - Query an Array of Embedded Documents"

In this MongoDB tutorial we will learn to query an array of embedded documents.

Login to your MongoDB server and insert the following documents.

For this tutorial I will insert the documents in the books collection.

> db.books.insertMany([
  {
    "title": "The C Programming Language",
    "author": ["Brian Kernighan", "Dennis Ritchie"],
    "inventory": [
      { "warehouse": "W1", "qty": 3000 },
      { "warehouse": "W2", "qty": 750 }
    ]
  },
  {
    "title": "MongoDB in Action",
    "author": ["Kyle Banker"],
    "inventory": [
      { "warehouse": "W2", "qty": 100 },
      { "warehouse": "W3", "qty": 1500 }
    ]
  },
  {
    "title": "Node.js in Action",
    "author": ["Marc Harter", "Nathan Rajlich", "T. J. Holowaychuk", "Mike Cantelon"],
    "inventory": [
      { "warehouse": "W1", "qty": 100 },
      { "warehouse": "W3", "qty": 250 }
    ]
  }

]);

Select based on exact match of embedded document in an array

In the following example we are fetching all the documents having the exact embedded document { "warehouse": "W1", "qty": 100 } in the inventory array.

Note! The field order is important i.e. the first field of the embedded document must be "warehouse" and must have value "W1" and the second field of the embedded document must be "qty" and must have value 100.

> db.books.find({ "inventory": { "warehouse": "W1", "qty": 100 } }).pretty();



{
  "_id" : ObjectId("5d2d9afd81a3cd0a9239c121"),
  "title" : "Node.js in Action",
  "author" : [
    "Marc Harter",
    "Nathan Rajlich",
    "T. J. Holowaychuk",
    "Mike Cantelon"
  ],
  "inventory" : [
    {
      "warehouse" : "W1",
      "qty" : 100
    },
    {
      "warehouse" : "W3",
      "qty" : 250
    }
  ]
}

If we change the field order of the embedded document in the query then we will not get the result.

In the following query we are changing the field order of the embedded document to { "qty": 100, "warehouse": "W1" } and it gives us no result.

> db.books.find({ "inventory": { "qty": 100, "warehouse": "W1" } }).pretty();

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