MySQL Conformance and Compatibility
1001
| 2 | LINESTRING(30220.2 15122.8,30217.2 15137.8,30207.6 15136, ... |
| 3 | LINESTRING(30179 15114.4,30176.6 15129.4,30167 15128,3016 ... |
| 4 | LINESTRING(30155.2 15121.4,30140.4 15118.6,30142 15109,30 ... |
| 5 | LINESTRING(30192.4 15085,30177.6 15082.2,30179.2 15072.4, ... |
| 6 | LINESTRING(30244 15087,30229 15086.2,30229.4 15076.4,3024 ... |
| 7 | LINESTRING(30200.6 15059.4,30185.6 15058.6,30186 15048.8, ... |
| 10 | LINESTRING(30179.6 15017.8,30181 15002.8,30190.8 15003.6, ... |
| 11 | LINESTRING(30154.2 15000.4,30168.6 15004.8,30166 15014.2, ... |
| 13 | LINESTRING(30105 15065.8,30108.4 15050.8,30118 15053,3011 ... |
| 21 | LINESTRING(30350.4 15828.8,30350.6 15845,30333.8 15845,30 ... |
| 22 | LINESTRING(30350.6 15871.4,30350.6 15887.8,30334 15887.8, ... |
| 23 | LINESTRING(30350.6 15914.2,30350.6 15930.4,30334 15930.4, ... |
| 24 | LINESTRING(30290.2 15823,30290.2 15839.4,30273.4 15839.4, ... |
| 25 | LINESTRING(30291.4 15866.2,30291.6 15882.4,30274.8 15882. ... |
| 26 | LINESTRING(30291.6 15918.2,30291.6 15934.4,30275 15934.4, ... |
| 154 | LINESTRING(30276.2 15143.8,30261.4 15141,30263 15131.4,30 ... |
| 155 | LINESTRING(30269.8 15084,30269.4 15093.4,30258.6 15093,30 ... |
| 157 | LINESTRING(30128.2 15011,30113.2 15010.2,30113.6 15000.4, ... |
| 249 | LINESTRING(30337.8 15938.6,30337.8 15946.8,30320.4 15946. ... |
+-----+---------------------------------------------------------------+
20 rows in set (0.46 sec)
12.16.7. MySQL Conformance and Compatibility
MySQL does not yet implement the following GIS features:
• Additional Metadata Views
OpenGIS specifications propose several additional metadata views. For example, a system view
named
GEOMETRY_COLUMNS
contains a description of geometry columns, one row for each
geometry column in the database.
• The OpenGIS function
Length()
[890]
on
LineString
and
MultiLineString
currently should
be called in MySQL as
GLength()
[992]
The problem is that there is an existing SQL function
Length()
[890]
that calculates the length
of string values, and sometimes it is not possible to distinguish whether the function is called in
a textual or spatial context. We need either to solve this somehow, or decide on another function
name.
12.17. Precision Math
MySQL 5.0 introduces precision math: numeric value handling that results in more accurate results
and more control over invalid values than in earlier versions of MySQL. Precision math is based on two
implementation changes:
• The introduction of SQL modes in MySQL 5.0 that control how strict the server is about accepting or
rejecting invalid data.
• The introduction in MySQL 5.0.3 of a library for fixed-point arithmetic.
These changes result in the following characteristics for numeric operations and provide improved
compliance with standard SQL:
• Precise calculations: For exact-value numbers, calculations do not introduce floating-point errors.
Instead, exact precision is used. For example, MySQL treats a number such as
.0001
as an exact
value rather than as an approximation, and summing it 10,000 times produces a result of exactly
1
,
not a value that is merely “close” to 1.
• Well-defined rounding behavior: For exact-value numbers, the result of
ROUND()
[913]
depends
on its argument, not on environmental factors such as how the underlying C library works.
• Platform independence: Operations on exact numeric values are the same across different
platforms such as Windows and Unix.
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