CODEWITHSUNDEEP
mysqlselecttextclojure
tazrmi
tazrmi

Reputation: 57

Get data from mysql database in clojure

I am trying to get some text from a database and use it in a function in clojure.

(defn getSelectedText [id]
    (j/query mysql-db
    ["select timesRead, text from news where id=?" id]))

When I println this it shows 

( {:timesRead 6, :text "Some text"})

When I try get to get the text from this it just doesn't work.

Do you have any idea how to change the getSelectedText function to get the text I need?

Upvotes: 0

Views: 635

Answers (2)

NielsK
NielsK

Reputation: 6956

When the resultset contains more records, you might want to take a look at the :row-fn and :result-set-fn parameters of clojure.java.jdbc/query to prevent copying all the of resultset before the connection is closed.

Processing inside the scope of the query fn / connection in this case would be done like

(defn getSelectedText [id]
  (j/query mysql-db
           ["select timesRead, text from news where id=?" id]
           :result-set-fn first  ;this fn should NOT be lazy
           :row-fn :text))

Upvotes: 1

user2524973
user2524973

Reputation: 1107

try 

(defn getSelectedText [id]
  (:text
    (first
      (j/query mysql-db
      ["select timesRead, text from news where id=?" id]))))

you're getting back a sequences of maps. first gives you the first item in the sequence, so then you have a map. :text says 'give me the value assigned to the :text key in the map'.

A note about retrieving values out of maps: what's interesting is that you can actually do either 

(:text my-map)

or

(my-map :text)

(also, the first form works with keywords (which start with the colon :) but not with keys that are strings; the jdbc library generally keywordizes column names for convenience)

Upvotes: 1

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