Updated mysqli version: if ($result = $mysqli->query(“SHOW TABLES LIKE ‘”.$table.”‘”)) { if($result->num_rows == 1) { echo “Table exists”; } } else { echo “Table does not exist”; } Original mysql version: if(mysql_num_rows(mysql_query(“SHOW TABLES LIKE ‘”.$table.”‘”))==1) echo “Table exists”; else echo “Table does not exist”; Referenced from the PHP docs.
The standard File module has the usual file tests available: RUBY_VERSION # => “1.9.2” bashrc = ENV[‘HOME’] + ‘/.bashrc’ File.exist?(bashrc) # => true File.file?(bashrc) # => true File.directory?(bashrc) # => false You should be able to find what you want there. OP: “Thanks but I need all three true or false” Obviously not. Ok, try … Read more
Why your code does not work? The where method returns an ActiveRecord::Relation object (acts like an array which contains the results of the where), it can be empty but it will never be nil. Business.where(id: -1) #=> returns an empty ActiveRecord::Relation ( similar to an array ) Business.where(id: -1).nil? # ( similar to == nil? … Read more
If the sent_at field is not there when its not set then: db.emails.count({sent_at: {$exists: false}}) If it’s there and null, or not there at all: db.emails.count({sent_at: null}) If it’s there and null: db.emails.count({sent_at: { $type: 10 }}) The Query for Null or Missing Fields section of the MongoDB manual describes how to query for null … Read more
Intuitive is …EXISTS (SELECT * .. because you really don’t care The only keyword of importance is EXISTS The choice of …EXISTS (SELECT 1 .. perpetuates the general myths and superstitions around EXISTS (eg comments on the MySQL docs). ANSI standard says “doesn’t matter” It’s more interesting to understand that EXISTS is a semi-join.
Your status-codes are also a collection, so use Contains: var allowedStatus = new[]{ “A”, “B”, “C” }; var filteredOrders = orders.Order.Where(o => allowedStatus.Contains(o.StatusCode)); or in query syntax: var filteredOrders = from order in orders.Order where allowedStatus.Contains(order.StatusCode) select order;
Simpler, shorter, faster: EXISTS. IF EXISTS (SELECT FROM people p WHERE p.person_id = my_person_id) THEN — do something END IF; The query planner can stop at the first row found – as opposed to count(), which scans all (qualifying) rows regardless. Makes a big difference with big tables. The difference is small for a condition … Read more
There are two relevant functions on POSIX systems: stat() and lstat(). These are used to find out whether a pathname refers to an actual object that you have permission to access, and if so, the data returned tells you what type of object it is. The difference between stat() and lstat() is that if the … Read more
If you don’t want to execute SQL directly, the best way is to use Any(). This is because Any() will return as soon as it finds a match. Another option is Count(), but this might need to check every row before returning. Here’s an example of how to use it: if (context.MyEntity.Any(o => o.Id == … Read more
Create a UNIQUE constraint on your subs_email column, if one does not already exist: ALTER TABLE subs ADD UNIQUE (subs_email) Use INSERT … ON DUPLICATE KEY UPDATE: INSERT INTO subs (subs_name, subs_email, subs_birthday) VALUES (?, ?, ?) ON DUPLICATE KEY UPDATE subs_name = VALUES(subs_name), subs_birthday = VALUES(subs_birthday) You can use the VALUES(col_name) function in the … Read more