Can Drupal do database query (select, update, delete) and show the result on the web with customed layout?

I may not be able to answer all of your questions, but one important module for you to look at is the Views module, which alongside CCK, is one of the most powerful modules for Drupal. Views is essentially a smart query builder... per your settings, filters, arguments, etc, Views builds you a custom list of nodes, fields from within nodes, taxonomy terms, users, and much more (Views 2 has these new features - version 1 for Drupal 5 and below could only interface with the node table). After your View is built, Views module provides you with template file code (which you copy/paste into files with specific names it provides you with so it knows which template to use for a given View). In Views 1 (for Drupal 5) this is done with the Views Theming Wizard. In Views 2, click on "Theme: Information", under the Basic Settings category.

When needed (either for some query you can't make with Views, or for performance) you can also run Views' queries manually (Views 2 makes this especially easy and prints out the SQL queries for you to just copy and paste). Views has built in caching options to speed things up though. The general recommendation seems to be, use Views if you can and make use of its incredible integration with countless other modules and great features, and only resort to custom queries when you must.

Almost all Drupal sites I know of, from the small ones to the large/popular, make use of the Views module. Here's one nice example of a Drupal site that makes significant use of Views, CCK, Panels 2, and Nodequeue module... http://myplay.com

I wrote some tips earlier today regarding theming CCK with the aid of Contemplate module: http://drupal.org/node/282225
And here is a lesson I wrote that helps walk through the combination use of CCK, Views, Panels, and Nodequeue (lesson is for making a custom home/front page, however the info applies to the modules overall): http://drupal.org/node/278181#comment-910575
Here's a lesson I wrote on making a simple View (for Views 1, but concepts are applicable): http://drupal.org/node/168752#comment-263585
Here's a helpful screencast that illustrates a lot of the new functionality in Views 2: http://www.masteringdrupal.com/screencast/new-features-in-views2
I've collected some good resources here as well: http://forums.neverside.com/post/806952/#post806952

Regarding importing your data into Drupal, there are some modules that can help, such as Node Import and User Import. Personally I found it to be the best (for me) to manually import the data directly from the command line (though this took a bit of learning about the various tables data needed to be imported into... the most important tables for basic content are node and node_revisions). My reason for SQL importing was mostly due to having a huge amount of data though (about 21,000 users, 95,000 nodes, and 711,000 comments).

There may be some additional import helper modules... my suggestion is to visit the main modules listing - you can open this giant list, and using the Find feature of your web browser, locate anything you're looking for on the page.

-- David
absolutecross.com

Let's say we want to do 3 things

1) Create an admin form that let's someone enter city information (population, latitude/longitude, state, unemployment, google map).
2) Create a page that shows a list of all cities in our database
3) Create a nicely laid out page to show the specific city information

This requires NO programming.

1) To do this you would create a new CCK type (called city) and add the appropriate fields to it.
2) You would create a view and set the field to Node:Title and use a filter of Node:Type -> City
3) You would create a template page called node-city.tpl.php, use CSS and all of the fields used in the City type to get a nicely laid out page, and put it in your themes/template/ folder.

It's super simple and really powerful - all with no programming required. Of course if you know programming it can get even more powerful.

There's essentially 2 ways to interact with the drupal db. Through the drupal ui-- in which case you create content types using cck fields and present queries via views. I'm not really familiar with the schema behind cck, but I don't think it's as simple as one table per content type. And anyway, in this case, you really don't have to worry about the db and the schema-- the modules and DAL handle that.

Also, contemplate isn't required, but it is a convenient way to get more control over page presentation. cck/contemplate/views/panels will give you virtually unlimited control over presentation through the ui.

However, you can also do whatever you want manually with php, sql, html, or any combination thereof. You can enter sql and code directly into pages and blocks. There's also many very useful drupal functions available via the drupal api.

You can also mix and match if you want. Since you're new to drupal but not php/sql, i would suggest doing things via the drupal UI at first. It's the best way to learn it and understand its advantages and disadvantages. Then you can decide how much you wish to takeover manually.

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