This blog post will deal with how you carry out simple SQL queries in MapInfo. A further blog post will deal with more complex SQL queries.

Simple queries relating to attributes and spatial positioning are actually very straightforward as the functionality is present in the SELECT dialogue box, from the QUERY menu. The QUERY menu also has a SQL SELECT menu which allows you to carry out more complicated SQL queries.

It leads you through building a query in a very simple fashion. as follows:

1. Choose the table that contains the data that you want to make your selection from - this is the drop down menu next to the 'Select Records From Table' which is at the top of the box.

2. Enter the expression that will choose your data next to 'That Satisfy Either' in the second line of the table. If you are struggling to build the expression that you require you can always press the ASSIST button and that will launch the expression builder that will walk you through building an expression.

3. From the dropdown box you need to tell MapInfo where to store the results of your query. The dropdown is next to the 'Store Results in Table' title.

4. You need to choose how you would like the results of your search ordered. This you do at the dropdown menu next to the 'Sort Results By Column' title.

5. You can choose if you want the results of your query to be automatically opened in a new window. You do this by checking the box next to 'Browse Results'.

6. Finally there is a checkbox for 'Find Results In Current Map Window'. If you tick this checkbox then it will automatically adjust the scale of the map that is currently open so that it shows all of the features that have been selected by the query.




The next blog post will be on using the Expression Builder when you are creating a query in MapInfo. This is what was mentioned in point 2 and brings in some SQL.

Today's blog post will be the first of a series that will speak about using the SQL query function within MapInfo to search through your data. For example how many points or items fall within a certain polygon area would be very useful when you have defined a custom area.

This blog post will just introduce SQL and a little about how to use it. Next week we will move onto more detail about how to use SQL within MapInfo.

SQL is Structured Query Language and a very widely used computer language to work with databases, be it inserting, manipulating or deleting data from a table or tables (containing the data) or search for specific subsets of the data from within those tables. 

If you learn how to use SQL it will be useful very widely with almost any database program you can think of including Microsoft Access, SQL Server, MySQL and Oracle databases. 

Although it can become far more complicated almost all SQL queries use  the following 4 main points in their construction.

SELECT (name of piece of data you are looking for) FROM (insert the name of the data table that contains the data you are selecting from) WHERE (this is optional but if you want to find all points larger than a certain figure this is where you add the constraint that you would like to impose) ORDER BY (this is where you add the order which you would like the data to be presented in, usually date order)  

So for example if a company wanted to know which of their employee's had brithday's during the month of September the query would run as follows.  

SELECT name FROM employee_table WHERE month = September ORDER BY date ascending

A full explanation of SQL is beyond this blog so we're going to leave our introduction to SQL there. This will hopefully give you a high level overview of SQL and so allow us to look further at the SQL search functionality that MapInfo contains over our next few blog posts.