[Firebird-docs] LangRef 2.5beta1 - a few suggestions
I may be way too late, or others may have noted these already. This is a few suggestions that I collected in February: == Document version: 0.901 P.13Integer Data Types BIGINT is defined as 64-bit integer, INTEGER is defined as 4-byte integer. SMALLINT reveals nothing about bits or bytes. Not very consistent, but maybe this is all according to SQL rules? The create table example for INTEGER contains CONSTRAINT INTEG_60 is this a good example? P.17Data Types for Dates and Times There are examples of the extract function (p.18) for TIME, but none for DATE. Extract functions for DATE are only mentioned in passing under TIMESTAMP (p.18). P.22Table 3.5. Maximum Index Lengths by Page Size and Character Size The text above the column header Maximum length of an indexed string for a character set, bytes/character should just be Bytes/character (for the numbers 1 thru 6 in the column sub-headers). P.30Table 3.8. Literals with Predefined Values of Date and Time A small glitch with the lines in the lower right of the table (or a pdf rendering problem?). P.31Shorthand Casts for Date and Time Data Types TIMESTAMP has been split over two lines as TIMES-TAMP. P.32Implicit Data Type Conversion << Implicit data conversion is not possible in Dialect 3 the CAST function is almost always required to avoid data type clashes. In Dialect 1, in many expressions, one type is implicitly cast to another without the need to use the CAST function. For instance, the following clause in a Dialect 1 SELECT statement is valid: WHERE DOC_DATE < '31.08.2014' and the string type will be cast to the date type implicitly. >> Valid in dialect 3 (as well as in dialect 1), I think. == I had a few more, but realized they were the product of my confusion :-/ -- Aage J. -- Transform Data into Opportunity. Accelerate data analysis in your applications with Intel Data Analytics Acceleration Library. Click to learn more. http://pubads.g.doubleclick.net/gampad/clk?id=278785111=/4140 ___ Firebird-docs mailing list Firebird-docs@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/firebird-docs
[Firebird-docs] LangRef 2.5beta1 - a few more suggestions /4
== p.87 Maybe a few words on the naming of "unnamed" constraints. create table TEST ( ID integer not null primary key ) The user might like to know that 2 constraints are created, called INTEG_n (f.ex. INTEG_157 (for "not null") and INTEG_158 (for "primary key")). And the (unique) index will be named rdb$primaryN (f.ex. rdb$primary66). p.104 Index Direction: Explain why the user might want to have the (non-default) descending index. Maybe that is more appropriate in an "User's Guide"? p.107 (Active option: How is it useful?) from: ... on the indexes of a large table in a database that is infrequently restored. to: ... on the indexes of a large table in a database that is frequenty updated and infrequently restored. (Maybe not really necessary?) ( I didn't know that ACTIVE will rebuild an active index - good to know! ) Any good advice on using "alter index ..." and "set statistics ..." when the table is in use? Is it ok, impossible, adviced against, or an absolute no-no? p.109 Index Selectivity Index statistics in Firebird are not automatically recalculated, either after a lot of data has been modified or under any other conditions. -> Index statistics in Firebird are not automatically recalculated, not after data has been modified or under any other conditions. (I don't like this sentence, but couldn't find a better one) It may be necessary to recalculate the selectivity of an index after inserting, updating or deleting a large number of records in the table, because the selectivity tends to become outdated. -> It may be advantageous to recalculate ... p.111 Updateable Views the SELECT statement contains no ORDER BY or GROUP BY or GROUP BY clause -> the SELECT statement contains no ORDER BY or GROUP BY clause Another completely different thing (on comparison operators): What about varchars with trailing blanks - how do these compare with chars and varchar (without trailing blanks)? Maybe this is not stuff for a LangRef, but for "User's Guide" or SQL tutorial? I have a feeling that this either has been mentioned already or it is covered already in the LangRef - I just couldn't find it now. == -- Aage J. -- ___ Firebird-docs mailing list Firebird-docs@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/firebird-docs
[Firebird-docs] LangRef 2.5beta1 - a few more suggestions /5
I'll have mostly non-Firebird things on my mind the next week, so I'm just unloading my latest comments now! == p.117 Add a sentence to make it clear when the trigger is fired: For mutation events, does the trigger fire at commit or at individual insert/update/delete. For two-phase-commit, it is described at p.122 (good!). p.119: "Declarations and embedded statements are terminated with semi-colons (;)." For statements with a begin...end block, no semi-colon is used. Simple "if": BEGIN IF (NEW.cust_no IS NULL) THEN NEW.cust_no = GEN_ID(cust_no_gen, 1); END But, with a block of statements: BEGIN IF (NEW.cust_no IS NULL) THEN BEGIN NEW.cust_no = GEN_ID(cust_no_gen, 1); END END p.248 reveals that "The BEGIN and END statements have no line terminators." This explains it, but: a) This is a trap for new users - please make a note around p.119 (about semi-colons). b) "line terminators"? "statement terminator" seems better. And "embedded statements" - are these just ordinary statements in the trigger? p.124 ALTER TRIGGER set_cust_no INACTIVE; Does this have immediate effect, even without a commit? If a user inactivates a trigger, does something and then activates the trigger - what is the effect for users (in the inactive periode)? And, is it really inactive (without a commit)? I believe there has been some confused/confusing discussions on the support list in the past on whether a user can have a trigger de-activated just for himself. (He cannot, IIRC) == -- Aage J. -- Find and fix application performance issues faster with Applications Manager Applications Manager provides deep performance insights into multiple tiers of your business applications. It resolves application problems quickly and reduces your MTTR. Get your free trial! http://pubads.g.doubleclick.net/ gampad/clk?id=1444514301=/ca-pub-7940484522588532 ___ Firebird-docs mailing list Firebird-docs@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/firebird-docs
[Firebird-docs] LangRef 2.5beta1 - a few suggestions /2b
A few more:
p.53 (top)
[ ] ( ) | ^ - + * % _ ? {
No "}" (terminating brace) ?
[:ALPHA:]: Latin letters a..z and A..z.
Should be: a..z and A..Z ?
p.57 Existential Predicates
... Existential predicates are so called because they use various
methods to test the existence of the value on the left side of the
predicate in the output results of subqueries on the right.
Using the first example:
SELECT *
FROM employee
WHERE EXISTS(SELECT *
FROM employee_project ep
WHERE ep.emp_no = employee.emp_no)
What is the "value on the left side of the predicate" and what is
"output result of subqueries on the right"?
It is not intuitive to me.
It seems to be better explained in the next paragraph, but the end is
not very clear:
... tests the fact of the existence of any number of matching rows
that is greater than none.
Would something like
... tests the existence of at least one matching row.
be simpler and clearer?
--
Aage J.
--
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Accelerate data analysis in your applications with
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