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SECTION 01 / 15
From cards to tables: rows, columns and IDs
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A table stores the same information as the cards in a more regular shape. One ordinary card becomes one row. Each field becomes a column. You already know these records from Weeks 1 and 2; only their arrangement is changing.
REAL COURSE DATA · FOLLOW THE PROCEDURE
Turn score cards into table rows
Read the current record, check the explanation, and watch the variables. Use Back to revisit any step.
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Find a value using a record and a field
| CardNo | Name | CityTown | Mathematics | Physics | Chemistry | Total |
|---|---|---|---|---|---|---|
| 0 | Bhuvanesh | Erode | 68 | 64 | 78 | 210 |
| 1 | Harish | Salem | 62 | 45 | 91 | 198 |
| 2 | Shashank | Chennai | 57 | 54 | 77 | 188 |
To find Harish’s Physics mark, locate his row using CardNo 1, then read the Physics column: 45. CardNo is an identifier. Sorting the rows changes a row’s position, but it must not change the identifier or the values belonging to that student.
Word cards work in the same way
REAL COURSE DATA · FOLLOW THE PROCEDURE
Turn word cards into table rows
Read the current record, check the explanation, and watch the variables. Use Back to revisit any step.
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Start at the first step. Watch the current row and the values we remember.
The word table has SerialNumber, Word, PartOfSpeech and LetterCount. SerialNumber 12 is considered, a Verb with LetterCount 10. Two occurrences of Monday are two rows, even though their Word values match. Keep SerialNumber when order matters.
The score table has 9 fields. Some lesson tables show only the columns needed for that example. A smaller display does not remove the other fields from the dataset.
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Is a column one student or one attribute?
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One attribute, such as Mathematics. A row describes one student.
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Does sorting make CardNo 0 become CardNo 1?
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No. Sorting changes position, not identity.
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Why are two Monday cards separate rows?
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They are separate occurrences at different positions in the paragraph.
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Which field tells you the length of considered?
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LetterCount, which is 10. SerialNumber 12 is its position identifier.