Introduction to SQL
Selecting and sorting data
Filtering
Ordering and commenting
Aggregating & calculating values
Joins and aliases
Figure 1
![Join Diagram for Example](../fig/left-join-articles-journals_40.png)
Figure 2
This figure shows the relations between the tables and helps to
visualise joining or linking the tables in the database: We will cover
relational database design in the
next episode. In addition to visual above, SQL
Join Types Explained Visually provides visual/animated examples
to help convey to learners what is happening in SQL
JOIN
s.
Saving queries
Database design
Figure 1
![OpenRefine DOAJ Sample Article Data](../fig/doaj-spreadsheet.png)
Figure 2
![Fields, Records, Values](../fig/field-record-value.png)
Figure 3
![Articles Database](https://user-images.githubusercontent.com/30397506/115917162-6cc7ef00-a43b-11eb-97af-16fe50caa6a6.png)
Figure 4
![Introducting inconsistencies and normalising data](../fig/normalisation.png)