Searching the Database by Tags

• This will require an AJAX query, whose format we just get to make up. For instance, we make the request with a URL like this:
  http:server162.site:####/query?keyList=castle+nature%20scene As before, we can teach the server to answer these requsts first, and then teach the browser to make them. Note that to URL-enclode a string with spaces and other special characters, we can use the Javascript function encodeURIComponent, and to decode it we can use decodeURIComponent.
• Use something like this SQL command to check the location column (containing the landmark tag) and the tags column for the desired tags:
  SELECT * FROM photoTags WHERE (location = "Castle" OR tags LIKE "%Castle%") AND (location = "Nature Scene" OR tags LIKE "%Nature Scene%") The percent signs match any string, just like the * in Unix.
• The database callback should call a function which puts together the http response. In the JSON which goes into the body of the response, you can add a "message" property, containing a string saying something like,
  These are all of the photos satisfying this query. If there are no photos satisfying the query, include only the message:
  These were no photos satisfying this query. With each photo, return its entire database record.
• To check the input, you might want to use a Javascript regular expression. For instance, the expression /[^a-z ]/.test(tag) returns false when the string tag contains characters other than lower-case digits and the space character.