<commit_before># Combining queries
The UNION operator is used to combine the result-set of two or more SELECT statements.

Notice that each SELECT statement within the UNION must have the same number of columns. The columns must also have similar data types. Also, the columns in each SELECT statement must be in the same order.

##Union
Get all the publishers and all the games and combine them together in 1 result.
We use limit because the list would be too long.
```sql
SELECT vend_id, prod_id, prod_price
FROM products
WHERE prod_price <= 5
UNION
SELECT vend_id, prod_id, prod_price
FROM products
WHERE vend_id IN (1001,1002);
```
```
+---------+---------+------------+
| vend_id | prod_id | prod_price |
+---------+---------+------------+
|    1003 | FC      |       2.50 |
|    1002 | FU1     |       3.42 |
|    1003 | SLING   |       4.49 |
|    1003 | TNT1    |       2.50 |
|    1001 | ANV01   |       5.99 |
|    1001 | ANV02   |       9.99 |
|    1001 | ANV03   |      14.99 |
|    1002 | OL1     |       8.99 |
+---------+---------+------------+
```
###Union All
```sql
SELECT vend_id, prod_id, prod_price
FROM products
WHERE prod_price <= 5
UNION ALL
SELECT vend_id, prod_id, prod_price
FROM products
WHERE vend_id IN (1001,1002);
```

```
+---------+---------+------------+
| vend_id | prod_id | prod_price |
+---------+---------+------------+
|    1003 | FC      |       2.50 |
|    1002 | FU1     |       3.42 |
|    1003 | SLING   |       4.49 |
|    1003 | TNT1    |       2.50 |
|    1001 | ANV01   |       5.99 |
|    1001 | ANV02   |       9.99 |
|    1001 | ANV03   |      14.99 |
|    1002 | FU1     |       3.42 |
|    1002 | OL1     |       8.99 |
+---------+---------+------------+
```<commit_msg>And another one gone... (#36)<commit_after># Combining queries
The UNION operator is used to combine the result-set of two or more SELECT statements.

Notice that each SELECT statement within the UNION must have the same number of columns. The columns must also have similar data types. Also, the columns in each SELECT statement must be in the same order.

##Union
Here the database will first return the rows where de price is lower or equal to 5. After that (in the same returned list) the database will return the rows where the vend_id is 1001 or 1002.
```sql
SELECT vend_id, prod_id, prod_price
FROM products
WHERE prod_price <= 5
UNION
SELECT vend_id, prod_id, prod_price
FROM products
WHERE vend_id IN (1001,1002);
```
```
+---------+---------+------------+
| vend_id | prod_id | prod_price |
+---------+---------+------------+
|    1003 | FC      |       2.50 |
|    1002 | FU1     |       3.42 |
|    1003 | SLING   |       4.49 |
|    1003 | TNT1    |       2.50 |
|    1001 | ANV01   |       5.99 |
|    1001 | ANV02   |       9.99 |
|    1001 | ANV03   |      14.99 |
|    1002 | OL1     |       8.99 |
+---------+---------+------------+
```
###Union All
`UNION ALL` does not remove duplicated records.
```sql
SELECT vend_id, prod_id, prod_price
FROM products
WHERE prod_price <= 5
UNION ALL
SELECT vend_id, prod_id, prod_price
FROM products
WHERE vend_id IN (1001,1002);
```

```
+---------+---------+------------+
| vend_id | prod_id | prod_price |
+---------+---------+------------+
|    1003 | FC      |       2.50 |
|    1002 | FU1     |       3.42 |  <- Same
|    1003 | SLING   |       4.49 |
|    1003 | TNT1    |       2.50 |
|    1001 | ANV01   |       5.99 |
|    1001 | ANV02   |       9.99 |
|    1001 | ANV03   |      14.99 |
|    1002 | FU1     |       3.42 |  <- Same
|    1002 | OL1     |       8.99 |
+---------+---------+------------+
```
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{'dir': 'git-commits-cleaned', 'id': '2851273', 'n_tokens_mistral': 1383, 'n_tokens_neox': 1161, 'n_words': 389}