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Submitting a SELECT query and getting the number of results

From: Accessing Databases with Object-Oriented PHP

Video: Submitting a SELECT query and getting the number of results

MySQL Improved uses a single method called The try block at the top of the page includes the connection To find out how many rows the result set contains, And then we just use our result object, and call its num_rows property.

Submitting a SELECT query and getting the number of results

MySQL Improved uses a single method called query to submit SQL statements to the database. When used with a select query, it returns a MySQLi result object. As well as containing the result set, the result object has a property indicating how many rows it contains. This is MySQLi_num_rows.php, which you can find in the chapter five 05_03 folder of the exercise files.

The try block at the top of the page includes the connection script and then runs a very simple SQL query, a select query. The body of the page contains a table where the results of the query will eventually be displayed. So let's submit the query. To do that, we simply need to call the query method and assign the result to an object. So we'll call the result object result equals db our connection, and then we just use the query method and pass it our SQL, our select query.

To find out how many rows the result set contains, we can access the num_rose property of the result object. So let's insert a new line just before the table is to be displayed. Put it down here on line 23. Scroll up a little bit so we can see things better. I will create a variable called numrows. And then we just use our result object, and call its num_rows property. Num_rows in the property has an underscore.

We can use this value not only to display the number of results, but also to control whether to display the table. So let's create a conditional statement. If not numrows. So if we've got no results, numrows will be 0. We can say that no results were found. But if we have got results, we can say how many there were and then display the table. So we need an else block. And inside the else block, we'll display the values of numrows, so we use a double-quoted string here.

And we need to move this closing curly brace of the else block, delete that from there, and it needs to go right down underneath the table. Now we got a PHP block, which is closing the database connection, so we can add it in there. We are not going to display the results in the table yet. Let's just find out if numrows works, so let's save that and test the page in a browser. Total results found, ten. And there is the table which will be ready to display them later.

But let's amend the select query so that we get no results. So let's go up to the select query and we need to add in a where clause. And I happen to know that the names table does not contain a name David, so we'll put that in there, and we'll save that, return to the browser and refresh. This time, no results found and the table is being hidden. So when you use the query method to submit a select query, the result set is returned as a MySQLi result object, which has a num_rows property that tells you the number of rows that were in the result set.

And you can use this property not only to display how many results there are, but also to control the output if the result is empty. The next step is to display the result.

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Accessing Databases with Object-Oriented PHP

47 video lessons · 2996 viewers

David Powers
Author

 
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  1. 13m 33s
    1. Welcome
      1m 4s
    2. What you should know before watching this course
      2m 8s
    3. Using the exercise files
      4m 56s
    4. Setting SQLite permissions
      1m 11s
    5. A quick primer on using PHP objects
      4m 14s
  2. 10m 12s
    1. Overview of PHP database APIs
      4m 5s
    2. Using prepared statements
      4m 24s
    3. Using transactions
      1m 43s
  3. 48m 57s
    1. Creating a database source name
      2m 3s
    2. Connecting to a database with PDO
      7m 27s
    3. Looping directly over a SELECT query
      3m 49s
    4. Fetching a result set
      8m 3s
    5. Finding the number of results from a SELECT query
      7m 14s
    6. Checking if a SELECT query contains results
      3m 32s
    7. Executing simple non-SELECT queries
      6m 2s
    8. Getting error messages
      7m 17s
    9. Using the quote() method to sanitize user input
      3m 30s
  4. 39m 51s
    1. Binding input and output values
      2m 36s
    2. Using named parameters
      9m 51s
    3. Using question marks as anonymous placeholders
      2m 35s
    4. Passing an array of values to the execute() method
      5m 20s
    5. Binding results to variables
      7m 53s
    6. Executing a transaction
      6m 54s
    7. Closing the cursor before running another query
      4m 42s
  5. 21m 20s
    1. Generating an array from a pair of columns
      2m 44s
    2. Setting an existing object's properties with a database result
      4m 42s
    3. Creating an instance of a specific class with a database result
      6m 1s
    4. Reusing a result set
      7m 53s
  6. 38m 14s
    1. Connecting to a database with MySQLi
      5m 57s
    2. Setting the character set
      1m 57s
    3. Submitting a SELECT query and getting the number of results
      4m 4s
    4. Fetching the result
      7m 35s
    5. Rewinding the result for reuse
      3m 20s
    6. Handling non-SELECT queries
      5m 27s
    7. Getting error messages
      5m 47s
    8. Sanitizing user input with real_escape_string()
      4m 7s
  7. 27m 49s
    1. Initializing and preparing a statement
      4m 17s
    2. Binding parameters and executing a prepared statement
      5m 55s
    3. Binding output variables
      5m 6s
    4. Executing a MySQLi transaction
      7m 5s
    5. Dealing with "commands out of sync" in prepared statements
      5m 26s
  8. 24m 7s
    1. Buffered and unbuffered queries
      4m 19s
    2. Using real_query()
      6m 1s
    3. Freeing resources that are no longer needed
      2m 31s
    4. Submitting multiple queries
      6m 41s
    5. Creating an instance of a class from a result set
      4m 35s
  9. 3m 31s
    1. PDO and MySQLi compared
      3m 31s

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