What is the difference between #LATERAL JOIN and a subquery in PostgreSQL
What is a #LATERAL join?
The LATERAL key word can precede a sub-SELECT FROM item. This allows the sub-SELECT to refer to columns of FROM items that appear before it in the FROM list. (Without LATERAL, each sub-SELECT is evaluated independently and so cannot cross-reference any other FROM item.)
🔗 [ https://stackoverflow.com/questions/28550679/what-is-the-difference-between-lateral-join-and-a-subquery-in-postgresql ]
The following relational database systems support the LATERAL JOIN syntax:
- #Oracle since 12c
- #PostgreSQL since 9.3
- #MySQL since 8.0.14
@javaCode☕️
What is a #LATERAL join?
The LATERAL key word can precede a sub-SELECT FROM item. This allows the sub-SELECT to refer to columns of FROM items that appear before it in the FROM list. (Without LATERAL, each sub-SELECT is evaluated independently and so cannot cross-reference any other FROM item.)
🔗 [ https://stackoverflow.com/questions/28550679/what-is-the-difference-between-lateral-join-and-a-subquery-in-postgresql ]
The following relational database systems support the LATERAL JOIN syntax:
- #Oracle since 12c
- #PostgreSQL since 9.3
- #MySQL since 8.0.14
@javaCode☕️
👍3
How to limit the SQL query result set to Top-N rows only
#SQL:
#PostgreSQL 8.3 and #MySQL:
#Oracle 11g and older versions:
@javaCode☕️
#SQL:
SELECT
title
FROM
post
ORDER BY
id DESC
FETCH FIRST 5 ROWS ONLY#PostgreSQL 8.3 and #MySQL:
SELECT
title
FROM
post
ORDER BY
id DESC
LIMIT 5#Oracle 11g and older versions:
SELECT *
FROM (
SELECT
title
FROM
post
ORDER BY
id DESC
)
WHERE ROWNUM <= 5@javaCode☕️
👍10🤯3👌1
Introduction to PostgreSQL
#PostgreSQL LAG() function provides access to a row that comes before the current row at a specified physical offset. In other words, from the current row the LAG() function can access data of the previous row, or the row before the previous row, and so on.
The LAG() function will be very useful for comparing the values of the current and the previous row.
more info…
@javaCode☕️
LAG() function:#PostgreSQL LAG() function provides access to a row that comes before the current row at a specified physical offset. In other words, from the current row the LAG() function can access data of the previous row, or the row before the previous row, and so on.
The LAG() function will be very useful for comparing the values of the current and the previous row.
more info…
@javaCode☕️
👍13
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