MySQL update table based on another tables value
UPDATE TABLE2 JOIN TABLE1 ON TABLE2.SERIAL_ID = TABLE1.SUBST_ID SET TABLE2.BRANCH_ID = TABLE1.CREATED_ID;
join
Join between tables in two different databases?
Yes, assuming the account has appropriate permissions you can use: SELECT <…> FROM A.table1 t1 JOIN B.table2 t2 ON t2.column2 = t1.column1; You just need to prefix the table reference with the name of the database it resides in.
MySQL: Quick breakdown of the types of joins [duplicate]
Based on your comment, simple definitions of each is best found at W3Schools The first line of each type gives a brief explanation of the join type JOIN: Return rows when there is at least one match in both tables LEFT JOIN: Return all rows from the left table, even if there are no matches … Read more
How to do joins in LINQ on multiple fields in single join
var result = from x in entity join y in entity2 on new { x.field1, x.field2 } equals new { y.field1, y.field2 }
Why isn’t SQL ANSI-92 standard better adopted over ANSI-89?
According to “SQL Performance Tuning” by Peter Gulutzan and Trudy Pelzer, of the six or eight RDBMS brands they tested, there was no difference in optimization or performance of SQL-89 versus SQL-92 style joins. One can assume that most RDBMS engines transform the syntax into an internal representation before optimizing or executing the query, so … Read more
Join tables with SUM issue in MYSQL
When you use multiple joins in the main query, you end up with a cross product of all the tables, so the sums get multiplied by the number of rows matching in another table. You need to move the sums into subqueries. SELECT last_name, first_name, DATE_FORMAT(LEAST(mil_date, tm_date), ‘%m/%d/%y’ ) AS dates, total, minutes FROM bhds_teachers … Read more
SQL join: selecting the last records in a one-to-many relationship
This is an example of the greatest-n-per-group problem that has appeared regularly on StackOverflow. Here’s how I usually recommend solving it: SELECT c.*, p1.* FROM customer c JOIN purchase p1 ON (c.id = p1.customer_id) LEFT OUTER JOIN purchase p2 ON (c.id = p2.customer_id AND (p1.date < p2.date OR (p1.date = p2.date AND p1.id < p2.id))) … Read more
What is the difference between Left, Right, Outer and Inner Joins? [duplicate]
Simple Example: Let’s say you have a Students table, and a Lockers table. In SQL, the first table you specify in a join, Students, is the LEFT table, and the second one, Lockers, is the RIGHT table. Each student can be assigned to a locker, so there is a LockerNumber column in the Student table. … Read more
1052: Column ‘id’ in field list is ambiguous
SQL supports qualifying a column by prefixing the reference with either the full table name: SELECT tbl_names.id, tbl_section.id, name, section FROM tbl_names JOIN tbl_section ON tbl_section.id = tbl_names.id …or a table alias: SELECT n.id, s.id, n.name, s.section FROM tbl_names n JOIN tbl_section s ON s.id = n.id The table alias is the recommended approach — … Read more
Difference between JOIN and INNER JOIN
They are functionally equivalent, but INNER JOIN can be a bit clearer to read, especially if the query has other join types (i.e. LEFT or RIGHT or CROSS) included in it.