Updating one column table another column

looks like a simple case but I'm confused: table_A column - date_A , primary key key_A table_B column - date_B, foreign key key_B I need to update every date_A with date_B.

I need to update each row of table_A with matching row from table_B. I don't mean to be *** about it but it may confuse others who's trying to search before posting their problem.

After each exercise, we provide the solution so you can check your answer.

CREATE TABLE `ips` ( `id` int(10) unsigned NOT NULL DEFAULT '0', `begin_ip_num` int(11) unsigned DEFAULT NULL, `end_ip_num` int(11) unsigned DEFAULT NULL, `iso` varchar(3) DEFAULT NULL, `country` varchar(150) DEFAULT NULL ) ENGINE=Inno DB CREATE TABLE `country` ( `countryid` tinyint(3) unsigned NOT NULL AUTO_INCREMENT, `name` varchar(50) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL, `ordering` smallint(5) unsigned NOT NULL DEFAULT '0', `iso` char(2) NOT NULL, PRIMARY KEY (`countryid`) ) ENGINE=Inno DB Using My SQL update multiple table syntax: 14.2.11 UPDATE Syntax Note that you have two different lengths and data types on your iso columns.

There are, in fact, two separate sets of ISO codes, 2-letter and 3-letter, so you may not in reality be able to join these columns: ISO 3166-1 The join condition There is a difference in behavior to my version - your version will set it to NULL if it's not found, mine will not alter an existing value if it's not matched. Also the execution plan may differ depending upon the [email protected] It's probably not a problem - when you add the new column, I'm assuming it will be NULL and also a foreign key, so invalid entries wouldn't be allowed anyway.

But it's hard to tell from what has been explicitly given in your question.

Thanks, Colby" id="ctl00_m_m_i_ctl00_gr_ctl05_bestanswerbody" class="textarea-bestanswerhidden" name="bestanswerbody" answerbody Id="3916931" / UPDATE TABLE A SET column1=SELECT (column2) FROM A But if source is the same table...

UPDATE TABLE A SET column1=column2" id="ctl00_m_m_i_ctl00_gr_ctl07_bestanswerbody" class="textarea-bestanswerhidden" name="bestanswerbody" answerbody Id="3919012" / select old_table.col1 into new_table from old_table select * from table_new Jack.mike" id="ctl00_m_m_i_ctl00_gr_ctl09_bestanswerbody" class="textarea-bestanswerhidden" name="bestanswerbody" answerbody Id="3919075" / I believe your SQL will create a table new_table with a copy of old_table's col1.

When you design relational expressions, you have to decide whether you want a single row to match multiple rows (in a one-to-many—1: M—relationship) or you want many rows to match a single row in the joined table (i.e., you want to update all rows).

There are 2 syntaxes for an update query in Oracle depending on whether you are performing a traditional update or updating one table with data from another table.

You can also perform more complicated updates in Oracle.

If the table you're updating appears more than once in the FROM clause, only one reference to the table can omit a table alias; all other references to the table must include a table alias.

If you need to update a column in one table based on the values in another, then you will need to figure out which column maps rows from one table to the other.

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