8e8d54f6be
Added the text in -line 11 -line 38 to 62 for simplification in understanding the 'WHERE' clause
92 lines
3.7 KiB
Markdown
92 lines
3.7 KiB
Markdown
---
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title: SQL Where Clause
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---
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# SQL Where Clause
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### `WHERE` Clause (and/or, `IN`, `BETWEEN`, and `LIKE`)
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The `WHERE` clause is used to filter the number of rows returned, based on one or more conditions provided by user.
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In this case all five of these will be used is a some what ridiculous `WHERE` clause.
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Here is the current full student list to compare to the `WHERE` clause result set:
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```sql
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select studentID, FullName, sat_score, rcd_updated from student;
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```
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```text
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+-----------+------------------------+-----------+---------------------+
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| studentID | FullName | sat_score | rcd_updated |
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+-----------+------------------------+-----------+---------------------+
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| 1 | Monique Davis | 400 | 2017-08-16 15:34:50 |
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| 2 | Teri Gutierrez | 800 | 2017-08-16 15:34:50 |
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| 3 | Spencer Pautier | 1000 | 2017-08-16 15:34:50 |
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| 4 | Louis Ramsey | 1200 | 2017-08-16 15:34:50 |
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| 5 | Alvin Greene | 1200 | 2017-08-16 15:34:50 |
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| 6 | Sophie Freeman | 1200 | 2017-08-16 15:34:50 |
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| 7 | Edgar Frank "Ted" Codd | 2400 | 2017-08-16 15:35:33 |
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| 8 | Donald D. Chamberlin | 2400 | 2017-08-16 15:35:33 |
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| 9 | Raymond F. Boyce | 2400 | 2017-08-16 15:35:33 |
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+-----------+------------------------+-----------+---------------------+
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9 rows in set (0.00 sec)
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```
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We 'd like to apply the following filters:
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* `WHERE` Student IDs are between 1 and 5 (inclusive)
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* `OR` studentID = 8
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```sql
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select studentID, FullName, sat_score, recordUpdated
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from student
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where (studentID between 1 and 5 or studentID = 8);
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```
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```text
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+-----------+----------------------+-----------+---------------------+
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| studentID | FullName | sat_score | rcd_updated |
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+-----------+----------------------+-----------+---------------------+
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| 1 | Monique Davis | 400 | 2017-08-16 15:34:50 |
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| 2 | Teri Gutierrez | 800 | 2017-08-16 15:34:50 |
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| 3 | Spencer Pautier | 1000 | 2017-08-16 15:34:50 |
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| 4 | Louis Ramsey | 1200 | 2017-08-16 15:34:50 |
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| 5 | Alvin Greene | 1200 | 2017-08-16 15:34:50 |
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| 8 | Donald D. Chamberlin | 2400 | 2017-08-16 15:35:33 |
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+-----------+----------------------+-----------+---------------------+
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6 rows in set (0.00 sec)
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```
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Here's an updated query, where any record that has a SAT score that's in the list (1000, 1400) will not be presented in addition to the above conditions:
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```sql
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select studentID, FullName, sat_score, recordUpdated
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from student
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where (studentID between 1 and 5 or studentID = 8)
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and
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sat_score NOT in (1000, 1400);
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```
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```text
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+-----------+----------------------+-----------+---------------------+
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| studentID | FullName | sat_score | rcd_updated |
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+-----------+----------------------+-----------+---------------------+
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| 1 | Monique Davis | 400 | 2017-08-16 15:34:50 |
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| 2 | Teri Gutierrez | 800 | 2017-08-16 15:34:50 |
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| 4 | Louis Ramsey | 1200 | 2017-08-16 15:34:50 |
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| 5 | Alvin Greene | 1200 | 2017-08-16 15:34:50 |
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| 8 | Donald D. Chamberlin | 2400 | 2017-08-16 15:35:33 |
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+-----------+----------------------+-----------+---------------------+
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5 rows in set (0.00 sec)
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```
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*As with all of these SQL things there is MUCH MORE to them than what's in this introductory guide.
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I hope this at least gives you enough to get started.
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Please see the manual for your database manager and have fun trying different options yourself.
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