Completed concept entry for Postgresql operators #4764

content/postgresql/concepts/operator-invocations/operator-invocations.md

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+---
+Title: 'Operator Invocations'
+Description: 'The execution of operations on data.'
+Subjects:
+  - 'Computer Science'
+  - 'Data Science'
+Tags:
+  - 'Data'
+  - 'Operators'
+  - 'PostgreSQL'
+CatalogContent:
+  - 'learn-sql'
+  - 'paths/data-science-foundations'
+---
+
+In PostgreSQL, **operator invocations** allow operations to be excuted on data in one or multiple tables in a database. They can be used to but are not limited to calculations, comparisons, joining and filtering. 
+
+Note: These are common operators, but there are many others avaiable to use. 
+
+## Syntax
+
+### Comparison Operators
+
+```pseudo
+--Equal
+SELECT * from table_name
+WHERE column1 = 'North';
+
+--Not Equal
+SELECT * from table_name
+WHERE column1 = column2;
+
+-- Greater Than (or Equal To)
+SELECT * from table_name
+WHERE column1 > 10;
+
+-- Less Than (or Equal To)
+SELECT * from table_name
+WHERE column1 < 1000;
+```
+
+### Logical Operators
+
+```pseudo
+-- And
+SELECT * from table_name
+WHERE column1 >= 10 AND  column1 <= 1000;
+
+-- Or
+SELECT * from table_name
+WHERE column1 = 'North' OR 'WEST';
+
+-- Not
+SELECT * from table_name
+WHERE NOT column1 = 'SOUTH';
+```
+
+
+## Example 1
+
+Here's an example of operator invocations on data in the table `animals`. 
+
+| `id` |  `name`  |  `species`  |  `gender`  | `age`  |
+| ---- | -------- | ----------- | ---------- | ------ |
+| 01   | Niko     | monkey      | female     | 3      |
+| 02   | Frank    | giraffe     | male       | 4      |
+| 03   | Lyn      | lion        | female     | 6      |
+| 04   | Tom      | elephant    | male       | 7      |
+
+
+```sql
+SELECT * from animals
+WHERE gender = 'female' AND age >= 4;
+```
+
+Output:
+
+| `id` |  `name`  |  `species`  |  `gender`  | `age`  |
+| ---- | -------- | ----------- | ---------- | ------ |
+| 03   | Lyn      | lion        | female     | 6      |
+
+
+## Example 2
+
+Using that same table, here is another operator invocation example.
+
+```sql
+SELECT * from animals
+WHERE NOT species = 'lion'; 
+```
+
+Output:
+
+| `id` |  `name`  |  `species`  |  `gender`  | `age`  |
+| ---- | -------- | ----------- | ---------- | ------ |
+| 01   | Niko     | monkey      | female     | 3      |
+| 02   | Frank    | giraffe     | male       | 4      |
+| 04   | Tom      | elephant    | male       | 7      |