tag Flashcards
What are the data types to choose from when creating database fields?
⚫️integer
⚫️float
⚫️date / time /Datetime
⚫️Char (FIXED length up to 8,000 characters)
⚫️Varchar (variable length string up to 8,000 characters )
⚫️Text (variable length string up to 2GB)
⚫️autonumber
What are flat file databases?
Stores sa single table of data inside a single text file
What are primary keys ?
A field that stores unique data for each record in a table.
What are some flat file database issues ?
🔵inconsistencies in the data , making it hard to search or sort the data
🔵redundant data, so the databases use more storage/memory than needed
What is a ‘flat file database “?
A database that has all the data stored in one table.
▪️Each record is identified as a new line
▪️flat file databases are often stored using a CSV (comma separated values )format
▪️each field is separated by a comma
What are relational databases ?
Contain multiple tables , each table is known as a relation. Each table has links to others known as relationships
What is a foreign key?
A field in a table that references the primary key of another table.
What is SQL?
Structured query language
The language allows you to create , query, update and delete data to and from databases
Write an SQL query to output all the first names of members and their memberID, who are male
- all normal PSEUDOCODE arithmetic and operational comparatives can be used
How do you select all the fields within a table to output
SELECT *
Wildcard
Write an SQL query to find all the fields of dogs that are older than four (including those that are 4) and whose colour contains the letter ‘B’
Sort this array called members into ascending order of town , up outputting the first name and memberID
Change the age of Molly from 5 to 6
Delete all the black spaniels from the table
Select the owner and dog names for all the four year old dogs
(Multiple tables )
Why are databases used?
They are used to store large amounts of data.
They make retrieving information easy and efficient
What are some advantages of flat file databases ?
All data in one table , so easier to set up and understand
What are some advantages of relational databases ?
🔵data is only stored in one place and then referenced. This means that to input , update or delete pieces of data, it only has to be done in one place which can prevent inconsistencies
🔵only storing the same price of dat once will also save storage space
🔵relational databases can be more secure , some tables can be made more confidential so only some users can see certain data (helps companies meet data protection laws)
What is a data redundancy?
Having the same piece of data stored in multiple places
How do you insert a full record into a table ?
How would insert bits of a record into a table ?
What is a record ?
The row of a table
What is a field ?
Columns of the table
How do relational databases eliminate data inconsistencies?
Since the data only has to be entered once, and can be referenced through other tables, there is less likely to be any inconsistencies such as spelling mistakes made when entering data in. This will reduce the amount of errors made when making queries
How do relational databases eliminate data redundancy?
Since the data can be referenced from other tables using foreign keys, the same pieces of data do not have to be repeated and stored in multiple places, there are no longer pieces of data that are being repeated unnecessarily
What is a computer system?
Two or more computers , that are CONNECTED together that are able to exchange data with each other. Allowing software and hardware to be shared.
What are the advantages of networks?
🟢communication eg: emails & text messages
🟢file sharing , eg: stored centrally and worked upon centrally
🟢hardware sharing , eg printers , making it more cost effective
🟢user account allow you to log in from any device
🟢installing software centrally , takes less time
What are some disadvantages of networks?
🟣expensive to set up as a lot of hardware is required. eg: NIC cards, switched , cables
🟣vulnerable to hacking and malware which can spread to networked computers
🟣hard to maintain and install , may require employing a specialist
Describe a PAN
Personal area network:
- very short range(few meters)
- cantered around 1 user
A network that is spread over a very small area used to connect personal devices
🟡don’t require additional hardware, can used them on the move
🟡often wireless technology eg: Bluetooth
Describe a LAN
Local area network
🟡small geographical area located on a single site
🟡wired or wireless
🟡owned an maintained by the organisation
Describe a WAN
Wide area network
🟡A combination of LANs in different geographical locations
🟡expensive as they need to hire infrastructure
🟡under collected or distributed ownership
What is a WLAN?
A wireless local area network
What is a wireless network?
A network that connect computers to a network through electromagnetic ☢️ radiation
What is a wired network?
Makes use of physical wire to connect computers to the network
Advantages wireless 🟢networks:
🟢Wireless are cheaper to set up.
🟢Wireless also requires less information and installation is automatic.
🟢wireless can add people more easily
Advantages of wired networks🔴
🔴wired have a larger transmission speed, higher bandwidth, more reliable
🔴wired are more secured. As physical connection is needed to intercept data
🔴wired have no interference from other Wireless networks or physical obstructions like walls
What is a NIC?
Network interface card, a piece of hardware inside a device that allows it to be connected to devices
What is a WAP?
Wireless access point
Needed in wireless networks
Basically a switch needed to connect devices wirelessly
What are switches?
Used to connect devices within a LAN to form a network
Device can access the switch simultaneously
What are routers?
Transmit data between different networks
Used to connect to the internet
Compare fibre optic cables and copper cables
Fibre: transmits dat as light.
More expensive but higher bandwidth
No interference and very large distance
Copper :
cheaper but have lower bandwidth
Describe a star topology
All devices are connected to a central switch or server, controlling the network. Can be wired or wireless
What is a node?
A device connected to a network
Star network pros and cons
✅if a device fails the network is unaffected
✅fewer data collisions as all devices can transmit data at the same time
✅easier to add devices
✅packets only sent to intended devices
❌expensive as it requires a switch and other hardware
❌problem with switch then the whole network is affected
Describe a bus network
Use a single ‘backbone ‘ cable to connect all devices.
Two terminator at the end to stop data reflections (interference)
Pros and cons of Bus networks
✅if one device fails the network remains unaffected
✅cheap to set up and maintain
✅not dependant on a switch
❌frequent data collisions slowing the network down
❌unsuitable for large networks as too many data collisions
❌network fails if the backbone cable is broken