I have several complex queries (using subqueries, etc...) and want to glue them together with OR or AND statement.
For example:
where1=table.where(...)
where2=table.where(...)
I would like something like
where3=where1.or where2
Next example doesn't work for me:
users.where(users[:name].eq('bob').or(users[:age].lt(25)))
because of I have several where(..) queries and I want to concatenate them.
In other words
I have 3 methods: first return first where, second-second, third - OR concatenation.
I must have able to use all 3 methods in my application and save DRY code
are you looking for the form:
users.where(users[:name].eq('bob').or(users[:age].lt(25)))
docs: https://github.com/rails/arel
users.where(users[:name].eq('bob').or(users[:age].lt(25))) is close, but you need to get the arel_table to specify the columns, e.g.
t = User.arel_table
User.where(t[:name].eq('bob').or(t[:age].lt(25)))
I know that for AND concatenation you can do:
users = User.where(:name => 'jack')
users = users.where(:job => 'developer')
and you get a concatenation with AND in SQL (try it with #to_sql at the end)
Other than that you can do:
where1=table.where(...)
where2=table.where(...)
where1 & where2
example:
(User.where(:name => 'jack') & User.where(:job => 'dev')).to_sql
=> "SELECT `users`.* FROM `users` WHERE `users`.`name` = 'jack' AND `users`.`job` = 'dev'"
Related
I am trying to build a case query with distinct count in cakephp 3.
This is the query in SQL:
select COUNT(distinct CASE WHEN type = 'abc' THEN app_num END) as "count_abc",COUNT(distinct CASE WHEN type = 'xyz' THEN app_num END) as "count_xyz" from table;
Currently, I got this far:
$query = $this->find();
$abc_case = $query->newExpr()->addCase($query->newExpr()->add(['type' => 'abc']),' app_num','string');
$xyz_case = $query->newExpr()->addCase($query->newExpr()->add(['type' => 'xyz']),'app_num','string');
$query->select([
"count_abc" => $query->func()->count($abc_case),
"count_xyz" => $query->func()->count($xyz_case),
]);
But I can't apply distinct in this code.
Using keywords in functions has been a problem for quite some time, see for example this issue ticket: https://github.com/cakephp/cakephp/issues/10454.
This has been somewhat improved in https://github.com/cakephp/cakephp/pull/11410, so that it's now possible to (mis)use a function expression for DISTINCT as kind of a workaround, ie generate code like DISTINCT(expression), which works because the parentheses are being ignored, so to speak, as DISTINCT is not a function!
I'm not sure if this works because the SQL specifications explicitly allow parentheses to be used like that (also acting as a whitespace substitute), or because it's a side-effect, so maybe check that out before relying on it!
That being said, you can use the workaround from the linked PR until real aggregate function keyword support is being added, ie do something like this:
"count_abc" => $query->func()->count(
$query->func()->DISTINCT([$abc_case])
)
This would generate SQL similar to:
(COUNT(DISTINCT(CASE WHEN ... END)))
How can I perform a query with multiple LIKE parameters?
For example, I have this string to search through:
"I like searching very much"
This is the code I currently use:
$searTerm = "like"
$this->db->or_like('list.description', $SearchTerm,'both');
But i want to search with 2 or 3 parameters. like this:
$searTerm = "like"
$searTerm1 = "much"
How can i perform this to get the same result?
You can simply repeat the like parameters on the active record. In your example you would do something like this:
$this->db->or_like('list.description', $searchTerm1);
$this->db->or_like('list.description', $searchTerm2);
$this->db->or_like('list.description', $searchTerm3);
...
This will just join each or_like with an AND in the WHERE clause.
Firstly, you need to define the array with like variables then, its very important to put the or_like statement above the where clause in order to make multiple 'OR' statements for like 'AND' the where clause.
Here is example:
$this->db->or_like(array('column_name1' => $k, 'column_name2' => $k))
$this->db->where($whereColumn, $whereValue)
You can use like group
$this->db->group_start()->like('column_name1', $value)
->or_group_start()
->like('column_name2', $value)
->group_end()
->group_end();
Using Sequel I'd like to create an UPDATE statement like the following (from Postgres docs)
UPDATE employees SET sales_count = sales_count + 1 FROM accounts
WHERE accounts.name = 'Acme Corporation'
AND employees.id = accounts.sales_person;
However, looking at the Sequel documentation it's not clear where there's any way to create the FROM clause.
Is there a way to do this?
Thanks!
OK, Ben Lee's answer got me going in the right direction. Solution:
DB[:employees].from(:employees, :accounts).
where(:accounts__name => 'Acme Corporation').
update_sql(:employees__sales_count => "employees.sales_count + 1".lit)
I'm a bit uncertain about the use of .lit here, but it does seem to do the trick. (Also, I'm using update_sql rather than update to produce the SQL output rather than running the command.)
Result, as desired:
UPDATE "employees"
SET "employees"."sales_count" = employees.sales_count + 1
FROM "accounts"
WHERE ("accounts"."name" = 'Acme Corporation')
Everybody else's answers have one tiny superfluous clause.
DB.from(:employees, :accounts).
where(:accounts__name => 'Acme Corporation').
update_sql(:employees__sales_count => "employees.sales_count + 1".lit)
If you're doing a from() with two tables, then the one inside the DB[...] is ignored.
Can you just use a regular join? It's not exactly your query, but it should accomplish your goals, right?
DB[:employees].left_outer_join(:accounts, :sales_person => :id).
where('accounts.name' => 'Acme Corporation').
update('employees.sales_count' => 'employees.sales_count' + 1)
How do I query distinct with MongoMapper? My query is:
subscribedToThread = Comment.where(:subscribe_thread => 1).all
But this will return many objects with the same user_id. I need to return just a distinct user_id. Is this possible?
I think you will need to drop down to the ruby driver in order to do this as I don't think you can do this with MongoMapper itself:
subscribedToThread = Comment.collection.distinct("user_id", {:subscribe_thread => 1})
Calling the collection method on a model returns the collection as would be provided by the Ruby driver directly so you can issue a distinct query using the syntax below:
collection.distinct(key, query = nil)
You can read more about it here
Yes, you can do so:
subscribedToThread = Comment.where(:subscribe_thread => 1).fields(:user_id).all.compact!.unique!
This will nil every field but user_id which you then uniq!,ie you remove all doubles and then compact! all nil
http://mongomapper.com/documentation/plugins/querying.html#fields
Try this
subscribedToThread = Comment.where(:subscribe_thread => 1).fields(:user_id).collect(&:user_id).uniq
It will show you list of uniq user_id
Per section 2.2 of rails guide on Active Record query interface here:
which seems to indicate that I can pass a string specifying the condition(s), then an array of values that should be substituted at some point while the arel is being built. So I've got a statement that generates my conditions string, which can be a varying number of attributes chained together with either AND or OR between them, and I pass in an array as the second arg to the where method, and I get:
ActiveRecord::PreparedStatementInvalid: wrong number of bind variables (1 for 5)
which leads me to believe I'm doing this incorrectly. However, I'm not finding anything on how to do it correctly. To restate the problem another way, I need to pass in a string to the where method such as "table.attribute = ? AND table.attribute1 = ? OR table.attribute1 = ?" with an unknown number of these conditions anded or ored together, and then pass something, what I thought would be an array as the second argument that would be used to substitute the values in the first argument conditions string. Is this the correct approach, or, I'm just missing some other huge concept somewhere and I'm coming at this all wrong? I'd think that somehow, this has to be possible, short of just generating a raw sql string.
This is actually pretty simple:
Model.where(attribute: [value1,value2])
Sounds like you're doing something like this:
Model.where("attribute = ? OR attribute2 = ?", [value, value])
Whereas you need to do this:
# notice the lack of an array as the last argument
Model.where("attribute = ? OR attribute2 = ?", value, value)
Have a look at http://guides.rubyonrails.org/active_record_querying.html#array-conditions for more details on how this works.
Instead of passing the same parameter multiple times to where() like this
User.where(
"first_name like ? or last_name like ? or city like ?",
"%#{search}%", "%#{search}%", "%#{search}%"
)
you can easily provide a hash
User.where(
"first_name like :search or last_name like :search or city like :search",
{search: "%#{search}%"}
)
that makes your query much more readable for long argument lists.
Sounds like you're doing something like this:
Model.where("attribute = ? OR attribute2 = ?", [value, value])
Whereas you need to do this:
#notice the lack of an array as the last argument
Model.where("attribute = ? OR attribute2 = ?", value, value) Have a
look at
http://guides.rubyonrails.org/active_record_querying.html#array-conditions
for more details on how this works.
Was really close. You can turn an array into a list of arguments with *my_list.
Model.where("id = ? OR id = ?", *["1", "2"])
OR
params = ["1", "2"]
Model.where("id = ? OR id = ?", *params)
Should work
If you want to chain together an open-ended list of conditions (attribute names and values), I would suggest using an arel table.
It's a bit hard to give specifics since your question is so vague, so I'll just explain how to do this for a simple case of a Post model and a few attributes, say title, summary, and user_id (i.e. a user has_many posts).
First, get the arel table for the model:
table = Post.arel_table
Then, start building your predicate (which you will eventually use to create an SQL query):
relation = table[:title].eq("Foo")
relation = relation.or(table[:summary].eq("A post about foo"))
relation = relation.and(table[:user_id].eq(5))
Here, table[:title], table[:summary] and table[:user_id] are representations of columns in the posts table. When you call table[:title].eq("Foo"), you are creating a predicate, roughly equivalent to a find condition (get all rows whose title column equals "Foo"). These predicates can be chained together with and and or.
When your aggregate predicate is ready, you can get the result with:
Post.where(relation)
which will generate the SQL:
SELECT "posts".* FROM "posts"
WHERE (("posts"."title" = "Foo" OR "posts"."summary" = "A post about foo")
AND "posts"."user_id" = 5)
This will get you all posts that have either the title "Foo" or the summary "A post about foo", and which belong to a user with id 5.
Notice the way arel predicates can be endlessly chained together to create more and more complex queries. This means that if you have (say) a hash of attribute/value pairs, and some way of knowing whether to use AND or OR on each of them, you can loop through them one by one and build up your condition:
relation = table[:title].eq("Foo")
hash.each do |attr, value|
relation = relation.and(table[attr].eq(value))
# or relation = relation.or(table[attr].eq(value)) for an OR predicate
end
Post.where(relation)
Aside from the ease of chaining conditions, another advantage of arel tables is that they are independent of database, so you don't have to worry whether your MySQL query will work in PostgreSQL, etc.
Here's a Railscast with more on arel: http://railscasts.com/episodes/215-advanced-queries-in-rails-3?view=asciicast
Hope that helps.
You can use a hash rather than a string. Build up a hash with however many conditions and corresponding values you are going to have and put it into the first argument of the where method.
WRONG
This is what I used to do for some reason.
keys = params[:search].split(',').map!(&:downcase)
# keys are now ['brooklyn', 'queens']
query = 'lower(city) LIKE ?'
if keys.size > 1
# I need something like this depending on number of keys
# 'lower(city) LIKE ? OR lower(city) LIKE ? OR lower(city) LIKE ?'
query_array = []
keys.size.times { query_array << query }
#['lower(city) LIKE ?','lower(city) LIKE ?']
query = query_array.join(' OR ')
# which gives me 'lower(city) LIKE ? OR lower(city) LIKE ?'
end
# now I can query my model
# if keys size is one then keys are just 'brooklyn',
# in this case it is 'brooklyn', 'queens'
# #posts = Post.where('lower(city) LIKE ? OR lower(city) LIKE ?','brooklyn', 'queens' )
#posts = Post.where(query, *keys )
now however - yes - it's very simple. as nfriend21 mentioned
Model.where(attribute: [value1,value2])
does the same thing