The usual way to create a geometry column is AddGeometryColumn, however I have to work with pre-existing columns, so I can't use that function (as far as I know).
Thanks to the PostGIS docs, I can already register the column in the "geometry_columns" table, however AddGeometryColumn seems to do more than create a column and add a row in geometry_columns, for example it adds checks on the column.
So my question is what: what do I need to do to register the column manually, besides adding a row in geometry_columns ?
(for example, is there a modified version AddGeometryColumn that works with an existing column ?)
The easiest way of doing it on existing columns is using the function Populate_Geometry_Columns:
https://postgis.net/docs/Populate_Geometry_Columns.html
In other words: The function you are asking for is already there :-)
HTH
Nicklas
As you said, AddGeometryColumn is only a handy shortcut for creating not only the column, but adding type checks and indexes. Of course, you can add these by hand to an existing column: you simply need to do the same things that the AddGeometryColumn does for you in a single command.
If you need to transfer one "regular" column to a "gis" column, why not use SELECT INTO for transfering the data?
Related
I have a database with lots of text that are all in capital letters and now should be converted into normal lower/upper case writing. This applies to technical stuff, for example
CIRCUIT BREAKER(D)480Y/277VAC,1.5A,2POL
This should be written circuit breaker(D)480Y/277VAC,1.5A,2POL
I think the only Approach is to have a list of word with the correct spelling and then do something like a Search & Replace.
Does anybody can give me a clue to Approach this in MS SQL?
You could do one of two things -
Write a simple script (in whichever language you are comfortable - eg: php, perl, python etc.,) that reads the columns from the DB, does the case-conversion and updates the values back into the DB.
The advantage of this would be that you will have greater flexibility and control on what you want to modify and how you wish to do it.
For this solution to work, you may need to maintain a dict/hash in the script, having the mapping of upper-case to lower-case keyword mapping.
The second probable solution, if you do not wish to write a separate script, would be to create a SQL function instead, that reads the corresponding rows/columns that need to be updated, performs the case-conversion and writes/updates it back into the DB.
This might be slightly inefficient, depending on how you implement the function. But it takes away the dependency of writing another script for you.
For this solution to work, you may need to maintain another table having the mapping of upper-case to lower-case keyword mapping.
Whichever you are more comfortable with.
Create a mapping table for dictionary. It could be temporary table within a session. Load the table with values and use this temporary table for your update. If you want this to be permanant solution to handle new rows coming in, then have permanent table.
CREATE TABLE #dictionaryMap(sourceValue NVARCHAR(4000), targetValue NVARCHAR(4000));
CREATE TABLE #tableForUpdate(Term NVARCHAR(4000));
INSERT INTO #dictionaryMap
VALUES ('%BREAKER%','breaker'),('%CIRCUIT%','circuit');
INSERT INTO #tableForUpdate
VALUES ('CIRCUIT BREAKER(D)480Y/277VAC,1.5A,2POL');
Perform the UPDATE to #tableForUpdate using WhileLoop in TSQL, using #dictionaryMap.
I'm trying to add data from a internal table to a custom one.
DATA: BEGIN OF TMP_CTRYGRP_T OCCURS 1000,
CTYGR TYPE /SAPSLL/CTYGR,
TEXT1 TYPE /SAPSLL/TEXT60,
END OF TMP_CTRYGRP_T.
SELECT ctygr, text1 FROM /SAPSLL/CTYGPT INTO TABLE #DATA(lt_countryGroupsTable)
LOOP AT lt_countryGroupsTable ASSIGNING FIELD-SYMBOL(<ls_countryGroups>).
APPEND <ls_countryGroups> TO TMP_CTRYGRP_T.
ENDLOOP.
Then I want to add the line in a custom Table Type ZZ_T_TAB
So I've tried to create a field-symbol of this table, creating an internal table from it, but none of the solutions I've tried was permitting me to add lines in that Custom table (even if the one in the program had the lines).
The problem I mainly encountered was:
are not mutually convertible in a Unicode program.
So my questions are:
Why does that error happen? Googling it didn't provide me an understandable answer
For the moment I'm using an internal table limited to 1000 rows. But I don't really know by advance the number of lines the search could provide. Is there any way to improve that?
How to add lines from any solution to my ZZ_T_TAB then? And afterwards how could I add other fields in the same table, for the rows already existing?
As some of you maybe understood, I'm quite a rookie in ABAP.
So if there's any useful link to understand all of that I would be happy if you can share it with me.
Why don't you directly select into the table?
Don't use OCCURS as it is declared obsolete and already forbidden in classes.
Declare your own structure as type and mark your custom internal table as TYPE STANDARD TABLE OF struct_type. This way, there will be no upper bounds
TYPES:
BEGIN OF struct_type,
CTYGR TYPE /SAPSLL/CTYGR,
TEXT1 TYPE /SAPSLL/TEXT60,
END OF struct_type.
DATA tmp_ctrygrp_t TYPE STANDARD TABLE OF struct_type WITH EMPTY KEY.
Why does that error happen? Googling it didn't provide me an
understandable answer
You cannot use APPEND with non-identical structures. You have to "convert" it before. Look up for the command MOVE-CORRESPODING in ABAP help (F1 on command in editor).
For the moment I'm using an internal table limited to 1000 rows. But I
don't really know by advance the number of lines the search could
provide. Is there any way to improve that?
Do not use OCCURS extension it is deprecated (as lausek wrote), old syntax.
How then to add lines from any solution to my ZZ_T_TAB ? And
afterwards how could I add other fields in the same table, for the
rows already existing?
You can modify a DB table various ways.:
1, Use UPDATE statement to directly update a field value.
2, Use MODIFY statement to modify field values from a (for example) pre-selected
structure.
Look up the UPDATE and MODIFY command in ABAP help, there are really helpful code examples.
Currently I have a database that stores boolean fields as VARCHAR(1) ('T' or 'F'). I want to replace these with BIT. The problem is that this would require a ton of changes in the program that uses the database. So I thought the logical step is to add a BIT field and replace the existing VARCHAR(1) field with a computed column that I access rather than accessing the BIT field (thus the program can continue to work as is without changes, and be changed to use the BIT field over time).
I know this won't work (UPDATE and INSERT doesn't work on computed columns). I know one option is to rename the existing table and add a view through which to access it, but I don't see that as a viable solution, as adding and removing columns, changing dependent views, etc. would be prone to errors (and it's not a neat solution in my opinion).
My question is - what are my options to achieve the above behaviour (such that the program can continue working as is)?
An example:
User (Active VARCHAR(1), ...)
Changed to use computed columns: (won't work)
User (Active_B BIT, Active AS CASE Active_B WHEN 1 THEN 'T' ELSE 'F' END, ...)
UPDATE: Fixed error in example.
It would have to be:
ALTER TABLE dbo.User
ADD Active AS CASE Active_B WHEN 1 THEN 'T' ELSE 'F' END PERSISTED
You need to use the column name (not the datatype) in the CASE. And I'd recommend making the computed column persisted, too - so that the value gets actually stored on disk (and not recomputed every time you access it).
An option is to have both a VARCHAR and a BIT field and use triggers to update between them.
I'll just have to figure out how to prevent infinite recursion (one idea is to have a field that serves no other purpose than to check if this trigger resulted from an update within another trigger (check if we're updating it and include it in the update in the trigger)). The updates need to go both ways to allow for easy backward compatibility.
If I have a POCO class with ResultColumn attribute set and then when I do a Single<Entity>() call, my result column isn't mapped. I've set my column to be a result column because its value should always be generated by SQL column's default constraint. I don't want this column to be injected or updated from business layer. What I'm trying to say is that my column's type is a simple SQL data type and not a related entity type (as I've seen ResultColumn being used mostly on those).
Looking at code I can see this line in PetaPoco:
// Build column list for automatic select
QueryColumns = ( from c in Columns
where !c.Value.ResultColumn
select c.Key
).ToArray();
Why are result columns excluded from automatic select statement because as I understand it their nature is to be read only. So used in selects only. I can see this scenario when a column is actually a related entity type (complex). Ok. but then we should have a separate attribute like ComputedColumnAttribute that would always be returned in selects but never used in inserts or updates...
Why did PetaPoco team decide to omit result columns from selects then?
How am I supposed to read result columns then?
I can't answer why the creator did not add them to auto-selects, though I would assume it's because your particular use-case is not the main one that they were considering. If you look at the examples and explanation for that feature on their site, it's more geared towards extra columns you bring back in a join or calculation (like maybe a description from a lookup table for a code value). In these situations, you could not have them automatically added to the select because they are not part of the underlying table.
So if you want to use that attribute, and get a value for the property, you'll have to use your own manual select statement rather than relying on the auto-select.
Of course, the beauty of using PetaPoco is that you can easily modify it to suit your needs, by either creating a new attribute, like you suggest above, or modifying the code you showed to not exclude those fields from the select (assuming you are not using ResultColumn in other join-type situations).
I want to know what columns where updated during update operation on a triger on first scaaning books online it looks like COLUMNS_UPDATED is the perfect solution but this function actualy don't check if values has changed , it check only what columns where selected in update clause, any one has other suggestions ?
The only way you can check if the values have changed is to compare the values in the DELETED and INSERTED virtual tables within the trigger. SQL doesn't check the existing value before updating to the new one, it will happily write a new identical value over the top - in other words, it takes your word for the update and tracks the update rather than actual changes.
We can use Update function to find if a particular column is updated:
IF UPDATE(ColumnName)
Refer to this link for details: http://msdn.microsoft.com/en-us/library/ms187326.aspx
As the others have posted, you'll need to interrogate INSERTED and DELETED. The only other useful bit of advice might be that you can get only the rows that have changed values (and discard the rows that didn't change) by using the EXCEPT operator - like this:
SELECT * FROM Inserted
EXCEPT
SELECT * FROM Deleted
The only way I can think of is that you can compare the values in DELETED and INSERTED to see which columns have changed.
Doesn't seem a particularly elegant solution though.
I asked this same question!
The previous posters are correct -- without directly comparing the values, you can't tell for sure whether the data has actually changed or not. However, there are several ways to do this type of checking, depending on what else you're trying to do in the trigger. My question has some good advice in the answers about those different mechanisms and their tradeoffs.