Foreign keys are almost always “Allow Duplicates,” which would make them unsuitable as Primary Keys. Instead, find a field that uniquely identifies each record in the table, or add a new field (either an auto-incrementing integer or a GUID) to act as the primary key. The only exception to this are tables with a one-to-one … Read more
I installed xampp,but when I tried to run it I got an error as thus: Error MySQL said: Documentation 1045 – Access denied for user ‘root’@’localhost’ (using password: NO) Connection for controluser as defined in your configuration failed. phpMyAdmin tried to connect to the MySQL server, and the server rejected the connection. You should check … Read more
For those arriving at this question because of the question title (as I did), this solved my problem: This error can indicate that the table’s PRIMARY KEY is not set to AUTO-INCREMENT, (and your insert query did not specify an ID value). To resolve: Check that there is a PRIMARY KEY set on your table, and that the … Read more
8 I use Mysql Workbench to connect my database,[ Hostname Port and Username are as shown in figure ,and password is right.When I click Test Connection ,it show as above.But if i use 3307 in place of 3306 as port,it connect sucessfully. What matter lead that and how I fix it? I use macbook pro … Read more
When dealing with null, = does not match the null values. You can use IS NULL or IS NOT NULL LIMIT can be used with UPDATE but with the row count only
When we refer to file-based databases we mean databases that we interact with/update directly (via an SQL abstraction offered by the JDBC driver) but in essence we just read/write to a file directly. Example would be SQLite No, CSV is a comma separated values file which allows data to be saved in a table structured … Read more
It’s better to use either of the following: The first alternative should give you no result or one result, the second count should be zero or one. How old is the documentation you’re using? Although you’ve read good advice, most query optimizers in recent RDBMS’s optimize SELECT COUNT(*) anyway, so while there is a difference … Read more
What is the complete list of all special characters for a SQL (I’m interested in SQL Server but other’s would be good too) LIKE clause? E.g. SQL Server: % _ [specifier] E.g. [a-z] [^specifier] ESCAPE clause E.g. %30!%%’ ESCAPE ‘!’ will evaluate 30% as true ‘ characters need to be escaped with ‘ E.g. they’re … Read more
Try doing this: