Re: [sqlite] Minor errors in CREATE TABLE syntax diagrams

[John Machin]

On 27/05/2009 12:33 AM, Jim Wilcoxson top-posted:
> For my money, I'd prefer to have a smaller, faster parser that worked
> correctly on correct input at the expense of not catching all possible
> syntax errors on silly input.

Firstly, none of the examples that I gave are syntactically incorrect.
Secondly, a compiler that doesn't reject ill-formed syntax should not be
seen after first semester CS101 -- the very idea is a nonsense.
Thirdly, all I'm asking for is a few more lines to make the diagrams 
accord with what the SQL compiler is already doing.

>  There is a definite trade-off here, and
> I could see where a totally complete parser that caught every possible
> error in SQL grammer might be twice the size of the entire SQLite code
> base.
> 
> Of course, you don't want an SQL syntax typo to trash your database
> either, without warning.

Which is why you test your software ... so col1 is not supposed to 
permit NULLs so you need to test it whether you wrote the syntactically 
correct "col1 INTEGER NOTE NULL, ..." or the equally syntactically 
correct "col1 INTEGER, ..." -- both being practically wrong.


>  I'm assuming the SQLite developers have made
> reasonable decisions about which parsing errors are important, and
> which aren't.

I hope they don't have any /parsing/ errors at all.


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Re: [sqlite] Minor errors in CREATE TABLE syntax diagrams

[Jim Wilcoxson]

For my money, I'd prefer to have a smaller, faster parser that worked
correctly on correct input at the expense of not catching all possible
syntax errors on silly input.  There is a definite trade-off here, and
I could see where a totally complete parser that caught every possible
error in SQL grammer might be twice the size of the entire SQLite code
base.

Of course, you don't want an SQL syntax typo to trash your database
either, without warning.  I'm assuming the SQLite developers have made
reasonable decisions about which parsing errors are important, and
which aren't.

Jim


On 5/26/09, John Machin  wrote:
>
> 1. SQLite allows NULL as a column-constraint.
>
> E.g. CREATE TABLE tname (col0 TEXT NOT NULL, col1 TEXT NULL);
>
> The column-constraint diagram doesn't show this possibility.
>
> Aside: The empirical evidence is that NULL is recognised and *ignored*;
> consequently there is no warning about sillinesses and typoes like in
> these examples of column-def:
> col1 INTEGER NOT NULL NULL
> col1 INTEGER NOTE NULL -- type="INTEGER NOTE", constraint="NULL"
>
> 2. According to the diagram for foreign-key-clause, there is no "express
> track" which allows skipping both "ON DELETE|UPDATE|INSERT etc" and
> "MATCH name". However SQLite does permit all of that to be skipped.
>
> E.g. CREATE TABLE tname(col0 TEXT PRIMARY KEY, col1 TEXT REFERENCES
> ftable(fcol));
>
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[sqlite] Minor errors in CREATE TABLE syntax diagrams

[John Machin]

1. SQLite allows NULL as a column-constraint.

E.g. CREATE TABLE tname (col0 TEXT NOT NULL, col1 TEXT NULL);

The column-constraint diagram doesn't show this possibility.

Aside: The empirical evidence is that NULL is recognised and *ignored*;
consequently there is no warning about sillinesses and typoes like in
these examples of column-def:
col1 INTEGER NOT NULL NULL
col1 INTEGER NOTE NULL -- type="INTEGER NOTE", constraint="NULL"

2. According to the diagram for foreign-key-clause, there is no "express
track" which allows skipping both "ON DELETE|UPDATE|INSERT etc" and
"MATCH name". However SQLite does permit all of that to be skipped.

E.g. CREATE TABLE tname(col0 TEXT PRIMARY KEY, col1 TEXT REFERENCES
ftable(fcol));

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