Hi guys I have the following code at some point of my trigger. (AFTER INSERT TRIGGER)
DECLARE Interv int;
At some point i use the following code:
SELECT myfield FROM TABLE WHERE interv=new.interv
But apparently the mysql confuses the value of two variables (NEW.INTERV AND INTERV) and don´t returns me the correct query's value.
But, if i use DECLARE Interv_Value int instead DECLARE Interv int the SELECT in question works fine.
Any ideas? I'm using MySQL 5.1.68.
What is confusing about this?
When you have the query:
SELECT myfield
FROM TABLE
WHERE interv = new.interv;
Then MySQL has to figure out where all unqualified names come from. It has some rules. In this case:
- First look at the columns in the `FROM` clause.
- Then it look in the environment
(These are actually scoping rules and also involve subqueries.) So, your query is interpreted as:
SELECT myfield
FROM TABLE
WHERE table.interv = new.interv;
As a general rule, write your queries using table aliases to specify where columns come from. So the above query could be written as:
SELECT myfield
FROM TABLE t
WHERE t.interv = new.interv;
Although you don't really want this version.
If you want to use variables, use user-defined variables with an # or give the variables names that are unlikely to conflict with column names (I use v_ prefixes for this).
Related
I'm working on a MySQL Way of printing an "affiliate tree" and got the thing working with Common Table Expression. I'm using the following code right now:
WITH RECURSIVE recUsers AS
(
SELECT ID, username, sponsorID, 1 AS depth, username AS path
FROM users
WHERE id = 1
UNION ALL
SELECT c.ID, c.username, c.sponsorID, sc.depth + 1, CONCAT(sc.path, ' > ', c.username)
FROM recUsers AS sc
JOIN users AS c ON sc.ID = c.sponsorID
)
SELECT * FROM recUsers;
This selects the tree underneath the user with the id 1.
Now what I'd need to get is a way to pass that id as a parameter, so I don't need to define everything from the beginning every time I want to get the result.. So my idea is to put everything in a stored prodecure and pass the id in as a parameter.. However, so far I didn't get it working and always getting various errors that are very self speaking...
Basically what I've tried was
DELIMITER //
CREATE PROCEDURE getAffiliateTree(IN userid INT())
BEGIN
---my code here, the userid 1 replaced with userid
END//
DELIMITER;
However, this doesn't seem to work.. How can I get this done?
Two things I would suggest:
Use INT, not INT(). The optional length argument to integer types is deprecated in MySQL 8.0 (which I know you're using, because you're using CTE syntax). Even if you did use the length argument, using an empty argument is not legal syntax.
Make sure that the userid input parameter name is distinct from all of the columns in the tables you reference. That is, if the table has a column named userid (any capitalization), then change the name of your input parameter. Otherwise you may make ambiguous expressions like:
... WHERE userid = userid
Even though you intend one of these to be the column and the other to be the parameter, the SQL parser has no way of knowing that. It ends up treating both as the column name, so it's trivially true on all rows of the table.
Actually, a third thing I would suggest: when you ask questions, "it doesn't seem to work" isn't clear enough. Did it produce an error? If so, what was the full error message? Did it produce no error, but didn't give you the result you wanted? If so, show a mocked-up example of what you expected, and what the query produced that didn't match. It helps to be as clear as you can when you post questions, so readers don't have to guess what trouble you need help with.
I've created a MySQL sproc which returns 3 separate result sets. I'm implementing the npm mysql package downstream to exec the sproc and get a result structured in json with the 3 result sets. I need the ability to filter the json result sets that are returned based on some type of indicator in each result set. For example, if I wanted to get the result set from the json response which deals specifically with Suppliers then I could use some type of js filter similar to this:
var supplierResultSet = mySqlJsonResults.filter(x => x.ResultType === 'SupplierResults');
I think SQL Server provides the ability to include a hard-coded column value in a SQL result set like this:
select
'SupplierResults',
*
from
supplier
However, this approach appears to be invalid in MySQL b/c MySQL Workbench is telling me that the sproc syntax is invalid and won't let me save the changes. Do you know if something like what I'm trying to achieve is possible in MySQL and if not then can you recommend alternative approaches that would help me achieve my ultimate goal of including some type of fixed indicator in each result set to provide a handle for downstream filtering of the json response?
If I followed you correctly, you just need to prefix * with the table name or alias:
select 'SupplierResults' hardcoded, s.* from supplier s
As far as I know, this is the SQL Standard. select * is valid only when no other expression is added in the selec clause; SQL Server is lax about this, but most other databases follow the standard.
It is also a good idea to assign a name to the column that contains the hardcoded value (I named it hardcoded in the above query).
In MySQL you can simply put the * first:
SELECT *, 'SupplierResults'
FROM supplier
Demo on dbfiddle
To be more specific, in your case, in your query you would need to do this
select
'SupplierResults',
supplier.* -- <-- this
from
supplier
Try this
create table a (f1 int);
insert into a values (1);
select 'xxx', f1, a.* from a;
Basically, if there are other fields in select, prefix '*' with table name or alias
It is possible?
DECLARE #vTableName varchar(50)
SET #vTableName = (SELECT TableName FROM qms_Types WHERE Id = 1)
SELECT * FROM #vTableName
I have this error:
Msg 1087, Level 16, State 1, Line 3 Must declare the table variable
"#vTableName".
Short answer: No.
Long answer: Noooooooooooooooooooooooooooooooooooooo. Use dynamic SQL if you have to, but if you're structuring your tables in a way where you don't know the table name ahead of time, it might benefit you to rethink your schema.
Here is a great resource for learning how to use dynamic SQL: The Curse and Blessings of Dynamic SQL
if you're trying to select from a table of that name, then you can do something like this:
DECLARE #vTableName varchar(50)
SET #vTableName = (SELECT TableName FROM qms_Types WHERE Id = 1)
EXECUTE('SELECT * FROM [' + #vTableName + ']')
my solution for this:
EXECUTE('SELECT * FROM ' + TableName + '')
It seems as though different folks are interpreting the OP differently.
I'm pretty sure the OP is asking for this type of concept / ability / maneuver...
"Put a table name into a variable and then use that variable as though it were a table name."
DECLARE #TableIWantRecordsFrom varchar(50)
-- ^^^^^^^^^^^^^^^^^^^^^^
SET #TableIWantRecordsFrom = (SELECT TableName FROM qms_Types WHERE Id = 1) -- (L1)
-- ^^^^^^^^^^^^^^^^^^^^^^
-- Let's say, at this point, #TableIWantRecordsFrom ... contains the text 'Person'
-- ^^^^^^^^^^^^^^^^^^^^^^
-- assuming that is the case then...
-- these two queries are supposed to return the same results:
SELECT top 3 fname,lname,mi,department,floor FROM Person
-- ^^^^^^
SELECT top 3 fname,lname,mi,department,floor FROM #TableIWantRecordsFrom -- (L2)
-- ^^^^^^^^^^^^^^^^^^^^^^
From reading all the responses and answers, it appears that this kind of maneuver can't be done - unless - you use dynamic SQL which...
can be a bit of a pain to create and maintain and
can be more work to create than the time it "saves" you in the future.
================================================================
There are other languages where this can be done... in literally, two lines of code (see (L1) and (L2) in above code) and not having to do a lot of formatting and editing.)
(I've done it before - there is another language where all you'd need is L1 and L2...)
================================================================
It is unfortunate that SQL Server will not do this without going to a decent amount of effort...
first write your SQL then
test it to make sure it does, in fact, work then
frame each line with tick marks and then escape your ticks that are now inside THOSE tick marks
declare the variable
set the variable to the sql statement you ticked above
(I may be missing some additional steps)
Oh, and then, if you ever need to maintain it
you need to either, be very careful and just edit it right there, as is, and hope you get it all just right -or- you may have saved a copy of it... un-ticked and un-variablized so you can edit the "real" sql and then when you're done you can RE DO these steps... again.
I think you want this:
DECLARE #vTableName table(TableName varchar(50))
insert into #vTableName
SELECT TableName FROM qms_Types WHERE Id = 1
SELECT * FROM #vTableName
The only way you can do this is through Dynamic SQL which refers to the practice of creating a T-SQL text and executing it using the sp_executesql (or simply exec)
Here is a helpful link about dynamic sql The Curse and Blessings of Dynamic SQL.
You should really think whether or not this is a case for dynamic sql or if there is another way for you to perform this operation.
Given SQL Server 2008, I have written a simple find in string function as follows:
ALTER FUNCTION [dbo].[FindInString]
(
#FindText VARCHAR(255),
#TextSource VARCHAR(512)
)
RETURNS INT
AS
BEGIN
DECLARE #Result INT
SET #Result = 0
SELECT #Result = CHARINDEX(#FindText, #TextSource)
RETURN #Result
END
The complexity of the find function may change in the future, which is why I wanted to encapsulate it in a function.
Now, when I only have one matching record in a table, this works:
SELECT #FindCount = dbo.FindInString('somestring', (SELECT TableSearch FROM Segments WHERE CID=22793))
However, when the select statement returns more than one, it makes sense as to why an error is thrown.
like to know is what I need to do to still have this work as a simple call, as above?
I only need to know if there is one match (I just need to know if #FindCount > 0), and I'm guessing some sort of a loop may be required, but would like to keep this as simple as possible.
Thanks.
You can use aggregate functions and one select:
select
#FindCount = sum(dbo.FindInString('somestring', TableSearch))
from
Segment
where
CID = 22793
Just take care with this, as FindInString will fire for each row, which can significantly reduce query performance. In this case, it's the only way to solve your problem, but just beware of the troubles that could arise.
The following doesn't work, but something like this is what I'm looking for.
select *
from Products
where Description like (#SearchedDescription + %)
SSRS uses the # operator in-front of a parameter to simulate an 'in', and I'm not finding a way to match up a string to a list of strings.
There are a few options on how to use a LIKE operator with a parameter.
OPTION 1
If you add the % to the parameter value, then you can customize how the LIKE filter will be processed. For instance, your query could be:
SELECT name
FROM master.dbo.sysobjects
WHERE name LIKE #ReportParameter1
For the data set to use the LIKE statement properly, then you could use a parameter value like sysa%. When I tested a sample report in SSRS 2008 using this code, I returned the following four tables:
sysallocunits
sysaudacts
sysasymkeys
sysaltfiles
OPTION 2
Another way to do this that doesn't require the user to add any '%' symbol is to generate a variable that has the code and exceute the variable.
DECLARE #DynamicSQL NVARCHAR(MAX)
SET #DynamicSQL =
'SELECT name, id, xtype
FROM dbo.sysobjects
WHERE name LIKE ''' + #ReportParameter1 + '%''
'
EXEC (#DynamicSQL)
This will give you finer controller over how the LIKE statement will be used. If you don't want users to inject any additional operators, then you can always add code to strip out non alpha-numeric characters before merging it into the final query.
OPTION 3
You can create a stored procedure that controls this functionality. I generally prefer to use stored procedures as data sources for SSRS and never allow dynamically generated SQL, but that's just a preference of mine. This helps with discoverability when performing dependency analysis checks and also allows you to ensure optimal query performance.
OPTION 4
Create a .NET code assembly that helps dynamically generate the SQL code. I think this is overkill and a poor choice at best, but it could work conceivably.
Have you tried to do:
select * from Products where Description like (#SearchedDescription + '%')
(Putting single quotes around the % sign?)
Dano, which version of SSRS are you using? If it's RS2000, the multi-parameter list is
not officially supported, but there is a workaround....
put like this:
select *
from tsStudent
where studentName like #SName+'%'
I know this is super old, but this came up in my search to solve the same problem, and I wound up using a solution not described here. I'm adding a new potential solution to help whomever else might follow.
As written, this solution only works in SQL Server 2016 and later, but can be adapted for older versions by writing a custom string_split UDF, and by using a subquery instead of a CTE.
First, map your #SearchedDescription into your Dataset as a single string using JOIN:
=JOIN(#SearchedDedscription, ",")
Then use STRING_SPLIT to map your "A,B,C,D" kind of string into a tabular structure.
;with
SearchTerms as (
select distinct
Value
from
string_split(#SearchedDescription, ',')
)
select distinct
*
from
Products
inner join SearchTerms on
Products.Description like SearchTerms.Value + '%'
If someone adds the same search term multiple times, this would duplicate rows in the result set. Similarly, a single product could match multiple search terms. I've added distinct to both the SearchTerms CTE and the main query to try to suppress this inappropriate row duplication.
If your query is more complex (including results from other joins) then this could become an increasingly big problem. Just be aware of it, it's the main drawback of this method.