I have a query similar to the following that I'd like to perform on an sqlite database:
SELECT name
FROM table
WHERE name LIKE "%John%"
ORDER BY (CASE WHEN name = "John" THEN 1 WHEN name LIKE "John%" THEN 2 ELSE 3 END),name LIMIT 10
I'd like to use SQLite for Swift to chain the query together, but I'm stumped as to how to (or if it is even possible to) use the .order method.
let name = "John"
let filter = "%" + name + "%"
table.select(nameCOL).filter(nameCOL.like(filter)).order(nameCOL)
Gets me
SELECT name
FROM table
WHERE name LIKE %John%
ORDER BY name
Any ideas on how to add to the query to get the more advanced sorting where names that start with John come first, followed by names with John in them?
I saw the sqlite portion of the solution here: SQLite LIKE & ORDER BY Match query
Now I'd just like to implement it using SQlite for Swift
Seems it may be too restrictive for that given the limited examples, anyone else have any experience with more complicated ORDER BY clauses?
Thanks very much.
Sqlite.swift can handle that pretty cleanly with two .order statements:
let name = "John"
let filter = "%" + name + "%"
table.select(nameCol).filter(nameCol.like(filter))
.order(nameCol.like("\(name)%").desc
.order(nameCol)
The .order statements are applied in the order they are listed, the first being primary.
The filter will reduce the results to only those with "John" in them. SQlite.swift can do many complex things. I thought I would need a great deal of raw sql queries when I ported 100s of complex queries over to it, but I have yet to use raw sql.
Related
I have a sql query suppose
sqlQuery="select * from %s_table where event like '%holi%'"
listCity=["Bangalore","Mumbai"]
for (city<- listCity){
print(s.format(city))
}
Expected output:
select * from Bangalore_table where event like '%holi%'
select * from Mumbai_table where event like '%holi%'
Actual output:
unknown format conversion exception: Conversion='%h'
Can anyone let me how to solve this, instead of holi it could be anything iam looking for a generic solution in scala.
If you want the character % in a formatting string you need to escape it by repeating it:
sqlQuery = "select * from %s_table where event like '%%holi%%'"
More generally I would not recommend using raw SQL. Instead, use a library to access the database. I use Slick but there are a number to choose from.
Also, having different tables named for different cities is really poor database design and will cause endless problems. Create a single table with an indexed city column and use WHERE to select one or more cities for inclusion in the query.
I'm using pg-promise and am not understanding how to run this query. The first query works, but I would like to use pg-promise's safe character escaping, and then I try the second query it doesn't work.
Works:
db.any(`SELECT title FROM books WHERE id = ANY ('{${ids}}') ORDER BY id`)
Doesn't work
db.any(`SELECT title FROM books WHERE id = ANY ($1) ORDER BY id`, ids)
The example has 2 problems. First, it goes against what the documentation tells you:
IMPORTANT: Never use the reserved ${} syntax inside ES6 template strings, as those have no knowledge of how to format values for PostgreSQL. Inside ES6 template strings you should only use one of the 4 alternatives - $(), $<>, $[] or $//.
Manual query formatting, like in your first example, is a very bad practice, resulting in bad things, ranging from broken queries to SQL injection.
And the second issue is that after switching to the correct SQL formatting, you should use the CSV Filter to properly format the list of values:
db.any(`SELECT title FROM books WHERE id IN ($/ids:csv/) ORDER BY id`, {ids})
or via an index variable:
db.any(`SELECT title FROM books WHERE id IN ($1:csv) ORDER BY id`, [ids])
Note that I also changed from ANY to IN operand, as we are providing a list of open values here.
And you can use filter :list interchangeably, whichever you like.
I have created one table with JSONB column as "data"
And the sample value of that column is
[{field_id:1, value:10},{field_id:2, value:"some string"}]
Now there are multiple rows like this..
What i want ?
I want to use aggregate function on "data" column such that, i should
get
Sum of all value where field_id = 1;
Avg of value where field_id = 1;
I have searched alot on google but not able to find a proper solution.
sometimes it says "Field doesn't exist" and some times it says "from clause missing"
I tried referring like data.value & also data -> value lastly data ->> value
But nothing is working.
Please let me know the solution if any one knows,
Thanks in advance.
Your attributes should be something like this, so you instruct it to run the function on a specific value:
attributes: [
[sequelize.fn('sum', sequelize.literal("data->>'value'")), 'json_sum'],
[sequelize.fn('avg', sequelize.literal("data->>'value'")), 'json_avg']
]
Then in WHERE, you reference field_id in a similar way, using literal():
where: sequelize.literal("data->>'field_id' = 1")
Your example also included a string for the value of "value" which of course won't work. But if the basic Sequelize setup works on a good set of data, you can enhance the WHERE clause to test for numeric "value" data, there are good examples here: Postgres query to check a string is a number
Hopefully this gets you close. In my experience with Sequelize + Postgres, it helps to run the program in such a way that you see what queries it creates, like in a terminal where the output is streaming. On the way to a working statement, you'll either create objects which Sequelize doesn't like, or Sequelize will create bad queries which Postgres doesn't like. If the query looks close, take it into pgAdmin for further work, then try to reproduce your adjustments in Sequelize. Good luck!
Using F# , FsSql and PostGres
So I'm using this function
let getSqlParameter value =
let uniqueKey = Guid.NewGuid().ToString("N")
let key = (sprintf "#%s" uniqueKey)
(key,Sql.Parameter.make(key,value))
to get me a parameter of anything I pass in dynamically
Which I then append to a query and I get something like this
select * from (select * from mytable) as innerQuery where #a29c575b69bb4629a9971dac2808b445 LIKE '%#9e3485fdf99249e5ad6adb6405f5f5ca%'
Then I take a collection of these and pass them off
Sql.asyncExecReader connectionManager query parameters
The problem that I'm having is that when I don't run this through my parameterization engine, it works fine. When I do, it doesn't work. It just returns empty sets.
The only thing I can think of is that the column names can't be parameterized. This is a problem because they're coming from the client. Is there a way to do this?
Okay so the answer here is that you can't parameterize column names as far as I can tell.
What I ended up doing was creating a whitelist of acceptable column names and then compare what was coming in to my whitelist. If it doesn't exist then I drop it.
By far a sub-optimal solution. I really wish there was a way to do this.
I am now working on the sqlite in iPhone platform and dealing with the database with some strange entities. One of the column in this DB called type, which allows multiple values (multiple types). The data in this column is like this:
1|9|20|31|999
The table is like:
ID TYPE
------------------------
1 1|9|20|31|999
2 5|13|15|30|990
3 6|7|45|46|57
When the user want to select the data with the type 9, it needs select the above data because the entity contains 9. And I use the following statement to execute:
SELECT id
FROM table
WHERE type LIKE '%' || ? || '%'
The problem is that the data with the type 999 and without type 9 will also be selected. Also, if the user wants to select type 1, the data with type 11, 12, 13...etc will also be selected.
I tried to use the statement:
SELECT id
FROM table
WHERE type LIKE '[^0123456789]' || ? || '[^0123456789]'
But it can't select any data.
What can I do to select the data with correct type?
(The database cannot be changed because of the company requirement)
You'd need a regular expression that matches only 'yournumber|', '|yournumber|', '|yournumber', or a combination of the above. I see no way an optimizer could use an index on that kind of thing short of a specialized index that would work similarly to full-text indexes.
This is almost hopeless, unless you have a trivial amount of data (or way too many processing resources), it will not scale.
If the amount of data is small, consider just selecting like '%number%', and do some post-processing in you application code.
Otherwise, normalize you data.
You could try this
SELECT id
FROM table
WHERE '|' + type + '|' LIKE '%|' + ? + '|%'
(I use the + operator here because it's easier to read but you could also use || instead)
It's an easy solution without regex. Indexes don't help anything here (this is the same for regex solution) the query will be slow with huge data.
I had a similar question I asked myself a while ago. Also check it's answer
I'm not too much familiar with SQLite but what about:
SELECT id FROM table WHERE type REGEX '(^9\|.*)|(.*\|9\|.*)|(.*\|9$)';
assuming that you are looking for the type 9
Then to look for type 999 it would be:
SELECT id FROM table WHERE type REGEX '(^999\|.*)|(.*\|999\|.*)|(.*\|999$)';
Note that you might want to tweak the expression if you may potentially have a single type value in the type field because in that case I'd suppose that there wouldn't be any | character.