> For the complete documentation index, see [llms.txt](https://docs.launchboard.app/cxd/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.launchboard.app/cxd/code-web-app-data-visualization/dashboard-template-tutorial/2-sql-introduction.md).

# 2 - SQL Introduction

[Structured Query Language (SQL)](https://www.w3schools.com/sql/sql_intro.asp) is a standard language for accessing and manipulating databases. Databases are just a group of data tables. Below is an example of a table called "Degrees" that could be in a database.

| Major                 | StartingMedianSalary | MidCareerMedianSalary |
| --------------------- | -------------------- | --------------------- |
| Accounting            | 46000.00             | 77100.00              |
| Aerospace Engineering | 57700.00             | 101000.00             |
| Agriculture           | 42600.00             | 71900.00              |
| Anthropology          | 36800.00             | 61500.00              |

We can then use SQL to "filter" the table. For example the following SQL statement..

```sql
SELECT Major, StartingMedianSalary FROM Degrees
```

would generate the following table.

| Major                 | StartingMedianSalary |
| --------------------- | -------------------- |
| Accounting            | 46000.00             |
| Aerospace Engineering | 57700.00             |
| Agriculture           | 42600.00             |
| Anthropology          | 36800.00             |

We simply `SELECT` columns `FROM` a table. Above we selected the columns "Major" and "StartingMedianSalary" from the "Degrees" table. 

We can also use `*` (a wild card) for the columns to get all the columns. So, `SELECT * FROM Degrees` will result in the full table. 

### Try It OUT

**1 - Find the following Javascript in your *****code.js***** file.**

```
viz.chart({
    sql:"SELECT * FROM Degrees",
    chartType:"Table",
    containerId:"chart2"
});
```

Notice how this code generates the table in your web view, where the table has a lot of columns (actually, all of them). 

**2 - Now change the SQL to the following to select only two columns.**

`SELECT Major, StartingMedianSalary FROM Degrees`

Run your web app and notice how the table has changed.

**3 - Now try the following SQL to get all the columns from a different table.**

 `SELECT * FROM States`

This gets a different table, "States", that can be found in our example database.

**4 - Go to** [**this Google Sheet**](https://docs.google.com/spreadsheets/d/1o60fGIa1USsQTXyYc-Qh-eYQ2TlHaaEC_iSdzJ7WbD4/edit?usp=sharing) **to see the example database and notice how each sheet (tab) is a table with a unique name.**

You will use SQL to get the right data from a database (Google Sheets file) for the charts you want to display. Next, let's look at producing the actual charts. 


---

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