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MYSQL Select MAX Date inside a join statement

Something like this… SELECT t1.received_id , t1.transaction_id , t1.date_modified , l.location FROM transactions t1 JOIN ( SELECT received_id, MAX(date_modified) maxmodify FROM transactions GROUP BY received_id) max_record ON max_record.received_id = t1.received_id AND max_record.maxmodify = t1.date_modified JOIN locations l ON l.location_id = t1.location_id JOIN received r ON r.received_id = t1.received_id WHERE t1.received_id = ‘1782’ ORDER BY t1.date_modified … Read more

CHECK constraint in MySQL is not working

MySQL 8.0.16 is the first version that supports CHECK constraints. Read https://dev.mysql.com/doc/refman/8.0/en/create-table-check-constraints.html If you use MySQL 8.0.15 or earlier, the MySQL Reference Manual says: The CHECK clause is parsed but ignored by all storage engines. Try a trigger… mysql> delimiter // mysql> CREATE TRIGGER trig_sd_check BEFORE INSERT ON Customer -> FOR EACH ROW -> BEGIN … Read more

conditional join in mysql

You can’t do it directly like that… you can do something like this though (not very pretty…): SELECT t.id, t.type, t2.id AS id2, t3.id AS id3 FROM t LEFT JOIN t2 ON t2.id = t.id AND t.type=”t2″ LEFT JOIN t3 ON t3.id = t.id AND t.type=”t3″

Why does MySQL report a syntax error on FULL OUTER JOIN?

There is no FULL OUTER JOIN in MySQL. See 7.2.12. Outer Join Simplification and 12.2.8.1. JOIN Syntax: You can emulate FULL OUTER JOIN using UNION (from MySQL 4.0.0 on): with two tables t1, t2: SELECT * FROM t1 LEFT JOIN t2 ON t1.id = t2.id UNION SELECT * FROM t1 RIGHT JOIN t2 ON t1.id … Read more

MySQL – Operand should contain 1 column(s)

Your subquery is selecting two columns, while you are using it to project one column (as part of the outer SELECT clause). You can only select one column from such a query in this context. Consider joining to the users table instead; this will give you more flexibility when selecting what columns you want from … Read more

MySQL – Subtracting value from previous row, group by

Working with MySQL variables is great, its like inline program variable assignments. First, the FROM clause “declares” the @ variables for you, defaulting to blank. Then query the records in the expected order you want them. It makes a single pass through the data instead of via repeated subqueries which can be time intensive. For … Read more

What does the KEY keyword mean?

Quoting from create-table – indexes andkeys {INDEX|KEY} So KEY is usually an INDEX KEY is normally a synonym for INDEX. The key attribute PRIMARY KEY can also be specified as just KEY when given in a column definition. This was implemented for compatibility with other database systems.

Binary Data in MySQL [closed]

The answer by phpguy is correct but I think there is a lot of confusion in the additional details there. The basic answer is in a BLOB data type / attribute domain. BLOB is short for Binary Large Object and that column data type is specific for handling binary data. See the relevant manual page … Read more

MySQL find_in_set with multiple search string

there is no native function to do it, but you can achieve your aim using following trick WHERE CONCAT(“,”, `setcolumn`, “,”) REGEXP “,(val1|val2|val3),”

Using union and order by clause in mysql

You can do this by adding a pseudo-column named rank to each select, that you can sort by first, before sorting by your other criteria, e.g.: select * from ( select 1 as Rank, id, add_date from Table union all select 2 as Rank, id, add_date from Table where distance < 5 union all select … Read more