SQL Comparison Keywords
There are other comparison keywords available in sql which are used to enhance the search capabilities of a sql query. They are "IN", "BETWEEN...AND", "IS NULL", "LIKE".
| Comparision Operators | Description |
|---|---|
| LIKE | column value is similar to specified character(s). |
| IN | column value is equal to any one of a specified set of values. |
| BETWEEN...AND | column value is between two values, including the end values specified in the range. |
| IS NULL | column value does not exist. |
SQL LIKE Operator
The LIKE operator is used to list all rows in a table whose column values match a specified pattern. It is useful when you want to search rows to match a specific pattern, or when you do not know the entire value. For this purpose we use a wildcard character '%'.
For example: To select all the students whose name begins with 'S'
SELECT first_name, last_name
FROM student_details
WHERE first_name LIKE 'S%';
The output would be similar to:
| first_name | last_name |
|---|---|
| ------------- | ------------- |
| Stephen | Fleming |
| Shekar | Gowda |
The above select statement searches for all the rows where the first letter of the column first_name is 'S' and rest of the letters in the name can be any character.
There is another wildcard character you can use with LIKE operator. It is the underscore character, ' _ ' . In a search string, the underscore signifies a single character.
For example: to display all the names with 'a' second character,
SELECT first_name, last_name
FROM student_details
WHERE first_name LIKE '_a%';
The output would be similar to:
| first_name | last_name |
|---|---|
| ------------- | ------------- |
| Rahul | Sharma |
NOTE:Each underscore act as a placeholder for only one character. So you can use more than one underscore. Eg: ' __i% '-this has two underscores towards the left, 'S__j%' - this has two underscores between character 'S' and 'i'.
SQL BETWEEN ... AND Operator
The operator BETWEEN and AND, are used to compare data for a range of values.
For Example: to find the names of the students between age 10 to 15 years, the query would be like,
SELECT first_name, last_name, age
FROM student_details
WHERE age BETWEEN 10 AND 15;
The output would be similar to:
| first_name | last_name | age |
|---|---|---|
| ------------- | ------------- | ------ |
| Rahul | Sharma | 10 |
| Anajali | Bhagwat | 12 |
| Shekar | Gowda | 15 |
SQL IN Operator:
The IN operator is used when you want to compare a column with more than one value. It is similar to an OR condition.
For example: If you want to find the names of students who are studying either Maths or Science, the query would be like,
SELECT first_name, last_name, subject
FROM student_details
WHERE subject IN ('Maths', 'Science');
The output would be similar to:
| first_name | last_name | subject |
|---|---|---|
| ------------- | ------------- | ---------- |
| Anajali | Bhagwat | Maths |
| Shekar | Gowda | Maths |
| Rahul | Sharma | Science |
| Stephen | Fleming | Science |
You can include more subjects in the list like ('maths','science','history')
NOTE:The data used to compare is case sensitive.
SQL IS NULL Operator
A column value is NULL if it does not exist. The IS NULL operator is used to display all the rows for columns that do not have a value.
For Example: If you want to find the names of students who do not participate in any games, the query would be as given below
SELECT first_name, last_name
FROM student_details
WHERE games IS NULL
There would be no output as we have every student participate in a game in the table student_details, else the names of the students who do not participate in any games would be displayed.
