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Changes for page SQL Query

Last modified by Danniar Firdausy on 2024/09/18 20:00
From version 4.1
edited by Erik Bakker
on 2022/08/30 15:02
Change comment: There is no comment for this version
To version 6.1
edited by Erik Bakker
on 2022/08/30 15:05
Change comment: There is no comment for this version

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1 1  {{container}}{{container layoutStyle="columns"}}(((
2 -= SQL Query =
3 -
4 4  In this microlearning, we will learn the basics of SQL queries. With the help of this information, you can start writing the correct queries to retrieve and write data from and to a database.
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6 6  Should you have any questions, please get in touch with [[academy@emagiz.com>>mailto:academy@emagiz.com]].
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47 47  
48 48  With a select statement, you read one or more records from the database. Within a select statement, you define the following:
49 49  
50 -* The columns you want to be returned (\* in case of all columns)
48 +* The columns you want to be returned (~* in case of all columns)
51 51  * The table from which to read
52 52  * Optional: A condition (WHERE x=x)
53 53  
54 -When combining all of this, you will end up, in the simplest form, with something like this: SELECT \* from mytable. Expanding on that, we could define that we only want to retrieve the id and contents column. To do so, we slightly alter our SQL query to this: SELECT id,contents from mytable. Building on that further, we could add a condition to the statement, a so-called where clause. With the help of that clause, we can even further narrow down our result set. An example of that would be SELECT id,contents from mytable WHERE id = :headers[id].
52 +When combining all of this, you will end up, in the simplest form, with something like this: SELECT ~* from mytable. Expanding on that, we could define that we only want to retrieve the id and contents column. To do so, we slightly alter our SQL query to this: SELECT id,contents from mytable. Building on that further, we could add a condition to the statement, a so-called where clause. With the help of that clause, we can even further narrow down our result set. An example of that would be SELECT id,contents from mytable WHERE id = :headers[id].
55 55  
56 56  {{info}}A SELECT statement never alters the state of the row in the database itself.{{/info}}
57 57