Combine Two SQL Rows into One: JOIN & UNION

You can use either JOIN clause or UNION clause to combine two lines into one.

If you have two tables, each with one row of data, you can combine them into one row using a JOIN clause. Here is an example:

Table 1:

id | name
---|------
1  | John

Table 2:

id | age
---|-----
1  | 25

The combined result:

id | name | age
---|------|-----
1  | John | 25

You can use the following SQL query to merge:

SELECT table1.id, table1.name, table2.age
FROM table1
JOIN table2 ON table1.id = table2.id;

If you want to merge two rows from two tables into one row, but there are no common columns to join on, you can use the UNION clause. Here is an example:

Table 1:

col1 | col2
-----|------
A    | 1

Table 2:

col3 | col4
-----|------
B    | 2

The combined result:

col1 | col2 | col3 | col4
-----|------|------|-----
A    | 1    |      |
     |      | B    | 2

You can merge using the following SQL query statement:

SELECT col1, col2, NULL AS col3, NULL AS col4
FROM table1
UNION ALL
SELECT NULL AS col1, NULL AS col2, col3, col4
FROM table2;

The above are two common methods of merging two lines into one, the specific way of merging depends on your data structure and requirements.