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Break up constrainst section to enhance readability

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Simon Holywell 2015-07-09 10:10:02 +01:00
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@ -298,7 +298,15 @@ changes to the definitions to keep them up to date.
Once the keys are decided it is possible to define them in the system using
constraints.
* All tables must have at least one key to be useful.
##### General
* Tables must have at least one key to be complete and useful.
* Constraints should be given a custom name excepting `UNIQUE`, `PRIMARY KEY`
and `FOREIGN KEY` where the database vendor will generally supply sufficiently
intelligible names automatically.
##### Layout and order
* Specify the primary key first right after the `CREATE TABLE` statement.
* Constraints should be defined directly beneath the column they correspond to.
Indent the constraint so that it aligns to the right of the column name.
@ -307,10 +315,13 @@ constraints.
include them at the end of the `CREATE TABLE` definition.
* If it is a table level constraint that applies to the entire table then it
should also appear at the end.
* Use alphabetical order so `ON DELETE` comes before `ON UPDATE`.
* All constraints should be given a custom name except `UNIQUE`, `PRIMARY KEY`
and `FOREIGN KEY` where the database vendor will generally supply sufficiently
intelligible names automatically.
* Use alphabetical order where `ON DELETE` comes before `ON UPDATE`.
* If it make sense to do so align each aspect of the query on the same character
position. For example all `NOT NULL` definitions should start at the same
character position.
##### Validation
* Use `LIKE` and `SIMILAR TO` constraints to ensure the integrity of strings
where the format is known.
* Where the ultimate range of a numerical value is known it must be written as a
@ -318,9 +329,8 @@ constraints.
truncation of data too large to fit the column definition. In the least it
should check that the value is greater than zero in most cases.
* `CHECK()` constraints should be kept in separate clauses to ease debugging.
* If it make sense to do so align each aspect of the query on the same character
position. For example all `NOT NULL` definitions should start at the same
character position.
##### Example
```sql
CREATE TABLE staff (