W3schools - SQL_SELECT / WHERE
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SELECT
Is used to select data from a database
The data returned is stored in a result table, called the result-set
Syntax
SELECT colum1, column2,…
FROM table_name;
-- if you want to select all the fields available in the table
SELECT * FROM table_name;
SELECT DISTINCT
Is used to return only distinct values
Syntax
SELECT DISTINCT column1, column2,…
FROM table_name;
-- Can count, It is not supported in MS Access
SELECT COUNT(DISTINCT column1,column2,…) FROM table_name;
-- Is the workaround for MS Access
SELECT Count(*) AS Distinctcolumn1
FROM (SELECT DISTINCT column1 FROM table_name);
WHERE
Is used filter records
Is used to extract only those records that fulfill a specified condition
Syntax
SELECT column1, column2,…
FROM table_name
WHERE condition;
SQL requires single quotes around text values
Numeric fields should not be enclosed in quotes
Operators in WHERE
WHERE clause can be combined with AND, OR, NOT operators
Syntax
SELECT column1, column2,…
FROM table_name
WHERE condition1 AND (condition2 OR condition3);
| Operator | Description |
|---|---|
| = | Equal |
| > | Greater than |
| < | Less than |
| >= | Greater than or equal |
| <= | Less than or equal |
| < > | Not equal, is some versions of SQL this operator may be != |
| BETWEEN ‘A’ AND ‘B’ | Between a certain range |
| LIKE ‘pattern’ | Search for a pattern |
| IN(value1,value2) | To specify multiple possible values for a column |
If you omit the WHERE clause, all records in the table will be apply
ORDER BY
Is used to sort the result-set in ascending or descending order
It sorts the records in ascending order by default
To sort the records in descending order, use the DESC keyword
Syntax
SELECT column1, column2,…
FROM table_name
ORDER BY column1, column2,…ASC|DESC;
-- Can use both, ORDER BY column1 ASC, column2 DESC;