Glossary
Data and SQL terms
20 terms
- Table
- Data arranged in rows and columns, like one sheet of a spreadsheet.
- Row
- One record in a table, such as one order.
- Column
- One property that every row has, such as the order date.
- Database
- An organised collection of tables that belong together.
- SQL
- The standard language for asking databases questions and changing their data.
- Query
- A question written in SQL.
- Primary key
- The column whose value identifies each row, such as an id.
- Foreign key
- A column that points at the primary key of another table.
- Join
- Combining rows of two tables that belong together.
- Filter
- Keeping only the rows that meet a condition, done with WHERE in SQL.
- Aggregate
- A value calculated from many rows, such as a count, sum or average.
- Group
- Rows that share a value and are summarised together with GROUP BY.
- NULL
- An empty value: nothing was recorded.
- CSV
- A plain text file of a table, with one row per line and commas between values.
- Data type
- The kind of value a column holds, such as text, number or date.
- Duplicate
- The same record entered more than once.
- Mean
- The sum of all values divided by how many there are.
- Median
- The middle value once all values are sorted.
- Outlier
- A value far away from the others.
- Normalisation
- Making values comparable before checking them, such as ignoring capital letters.