Is there an equivalent to the nameof operator in languages like C#, Java, etc for any SQL database implementations, in particular SQL Server?
If not, is there an equivalent function that can be rolled that will pass back a string (VARCHAR, etc) of a given object (for example, [dbo].[MyTable]) which is passed to it?
To get the name of an object, you can pass the ID.
You can get the ID from the name of the object.
Not sure if this is what you are looking for:
select object_name(object_id('my_table_name'))
Related
Folks
I am in the process of moving a decade old back-end from DB2 9.5 to Oracle 19c.
I frequently see in SQL queries and veiw definitions bizarre timestamp(nullif('','')) constructs used instead of a plain null.
What is the point of doing so? Why would anyone in their same mind would want to do so?
Disclaimer: my SQL skills are fairly mediocre. I might well miss something obvious.
It appears to create a NULL value with a TIMESTAMP data type.
The TIMESTAMP DB2 documentation states:
TIMESTAMP scalar function
The TIMESTAMP function returns a timestamp from a value or a pair of values.
TIMESTAMP(expression1, [expression2])
expression1 and expression2
The rules for the arguments depend on whether expression2 is specified and the data type of expression2.
If only one argument is specified it must be an expression that returns a value of one of the following built-in data types: a DATE, a TIMESTAMP, or a character string that is not a CLOB.
If you try to pass an untyped NULL to the TIMESTAMP function:
TIMESTAMP(NULL)
Then you get the error:
The invocation of routine "TIMESTAMP" is ambiguous. The argument in position "1" does not have a best fit.
To invoke the function, you need to pass one of the required DATE, TIMESTAMP or a non-CLOB string to the function which means that you need to coerce the NULL to have one of those types.
This could be:
TIMESTAMP(CAST(NULL AS VARCHAR(14)))
TIMESTAMP(NULLIF('',''))
Using NULLIF is more confusing but, if I have to try to make an excuse for using it, is slightly less to type than casting a NULL to a string.
The equivalent in Oracle would be:
CAST(NULL AS TIMESTAMP)
This also works in DB2 (and is even less to type).
It is not clear why - in any SQL dialect, no matter how old - one would use an argument like nullif('',''). Regardless of the result, that is a constant that can be calculated once and for all, and given as argument to timestamp(). Very likely, it should be null in any dialect and any version. So that should be the same as timestamp(null). The code you found suggests that whoever wrote it didn't know what they were doing.
One might need to write something like that - rather than a plain null - to get null of a specific data type. Even though "theoretical" SQL says null does not have a data type, you may need something like that, for example in a view, to define the data type of the column defined by an expression like that.
In Oracle you can use the cast() function, as MT0 demonstrated already - that is by far the most common and most elegant equivalent.
If you want something much closer in spirit to what you saw in that old code, to_timestamp(null) will have the same effect. No reason to write something more complicated for null given as argument, though - along the lines of that nullif() call.
I am using jOOQ to execute arbitrary SQL queries. I am doing this as following:
String result = create.fetchSingle("SELECT ...").getValue(0, String.class);
This query always returns one row and one column, hence the usage of fetchSingle and getValue(0, T). I could not find a method which combines the two.
I now want to pass a named parameter to that query. The parameter is used at several places, so I thought using a named parameter was a good usage here. The type of this parameter is an array of strings.
How can I do this? How do I refer to that parameter in the query? In JDBC, I would write :name_of_parameter::text[].
The API you're looking for is DSLContext.fetchSingle(String, Object...), which accepts a SQL string with parameter placeholders, as well as the actual bindings.
However, it does not support named parameters, only indexed parameters, so you'll have to repeat the value several times, e.g.
create.fetchSingle("SELECT 'a' WHERE ?::text[] = ?::text[]", value, value)
.getValue(0, String.class);
I'm creating a function for querying a SQLite database that should be generic in the sense of reading from multiple pre-defined tables. As part of the function's paremeters, it is necessary to tel which column of the table should be read, an info that is supposed to be passed by an enumerator value. So the call would be something like this:
callMyFunction(enumTableA,enumColumnB);
Since enumColumnB is an enumerator value, the argument is an integer and I would like to identify the column by that integer value without having to use a switch-case for that. Something like this:
SELECT column(enumColumnB) from ...
So instead of passing the name of the column or reading all columns with * and then selecting the desired one when reading, it would use the number of the column as passed by the enumerator value to identify what should be read.
Is it possible to do this for SQLite? I couldn't find any tutorial mentioning such possibility, so I'm almost concluding there is no such possibility (and I'll have to pass the name of the column as argument or use a switch-case at the end), but I'ld like to be sure I don't have this option available.
SQLite has no mechanism for indirect columns.
(SQLite is designed as an embedded database, i.e., to be used together with a 'real' programming language.)
You have to replace the column name in whatever programming language you're using.
I am creating a database in which certain derived attributes are computed using the Universal Gravitational Constant (G), whose approximate value is 6.673 * 10^-11.
I understand that a normal integer constant can be defined using a scalar function as follows
CREATE FUNCTION MY_CONST()
RETURNS INT
AS
BEGIN
RETURN 123456789
END
Thing is, I'm new to SQL and not sure how to store a complex value such as G in there. In popular high-level programming languages like Java, I usually define the value as 6.673e-11 at the top of the editor and call it whenever I need it in my calculations. I would like to know how to simply do the same in SQL.
I really just don't get how to translate the value into SQL code as a constant.
Oracle has a function called translate that can be used to replace individual characters of the string by others, in the same order that they appear. It is different than the replace function, which replaces the entire second argument occurence by the entire third argument.
translate('1tech23', '123', '456'); --would return '4tech56'
translate('222tech', '2ec', '3it'); --would return '333tith'
I need this to implement a search on a SQLite database ignoring accents (brazilian portuguese language) on my query string. The data in the table that will be queried could be with or without accents, so, depending on how the user type the query string, the results would be different.
Example:
Searching for "maçã", the user could type "maca", "maça", "macã" or "maçã", and the data in the table could also be in one of the four possibilities.
Using oracle, I would only use this:
Select Name, Id
From Fruits
Where Translate(Name, 'ãç','ac') = Translate(:QueryString, 'ãç','ac')
... and these other character substitutions:
áéíóúÁÉÍÓÚàèìòùÀÈÌÒÙãõÃÕäëïöüÄËÏÖÜâêîôûÂÊÎÔÛñÑçÇ
by:
aeiouAEIOUaeiouAEIOUaoAOaeiouAEIOUaeiouAEIOUnNcC
Of course I could nest several calls to Replace, but this wouldn't be a good choice.
Thanks in advance by some help.
Open-source Oracle functions for SQLite have been written at Kansas State University. They include translate() (full UTF-8 support, by the way) and can be found here.
I don't believe there is anything in sqlite that will translate text in a single pass as you describe.
This wouldn't be difficult to implement as a user defined function however. Here is a decent starting reference.
I used replace
REPLACE(string,pattern,replacement)
https://www.sqlitetutorial.net/sqlite-replace-function/