Posts tagged mysql
Subtag of sql
I had three data with where gender=female. I was trying to call those data with limit and offset (Since in future there might be more than 1000 data). SELECT * FROM `users` WHERE `gender`='Female'...
I have the following scenario (in MySQL 8): CREATE TABLE `steps` ( `id` int NOT NULL AUTO_INCREMENT, `number` varchar(30) DEFAULT NULL, `parent_number` varchar(30) DEFAULT NULL, `timestamp` ti...
Let's say I have a table with 10,000 rows and instead of selecting all of the rows at once I select 1,000 at a time like LIMIT 0,1000 LIMIT 1000,1000 etc. Without an ORDER BY statement the or...
I am building an MVC cart system. I have the MERCHANTS table and the PRODUCTS table. A merchant (store) can have one or more products, everything works fine but what I want is to display products b...
I have a column that is a concatenation of 5 other columns plus a join to a different table. UPDATE db.a JOIN db.b ON fk_b = b.pk SET concat_field = CONCAT(field1,field2,field3,b.field,field4,fi...
I had installed mysql using the following command sudo pacman -Sy mysql Earlier, I was using Lampp(Xampp for Linux) where I could start using the command /opt/lampp/start start I am not sur...
In some situations, could it be problematic to migrate a website's database (MySQL) from one website hosting provider to another without the information schema or with the information schema? In m...
For my purposes, it is secure enough to use passwords to execute MySQL commands on the command line, what I would like to do is disable the warning that says, mysql: [Warning] Using a password on ...
Its possible to execute a MySQL file from the command line like so, mysql -u USER -pPASSWORD < FILENAME which triggers a warning, mysql: [Warning] Using a password on the command line int...
In a stored procedure let's say I have a VARCHAR variable, DECLARE example_variable VARCHAR(100); how much memory is allocated to it and is that independent of the length of the data in the var...
Lets say I have two tables, A and B and I need to join a subset of them. Is there best practices of sticking the conditions in the WHERE clause like this, SELECT * FROM A JOIN B on a.fk_b = b....
Due to a series of unfortunate events I have some tables where the auto_increment value got behind what it should be. If the auto_increment value is 9 and there are 20 rows in the table the next 1...
I have a PHP program that does a SELECT and then updates some of the values based on an algorithm. Rather than updating one row at a time UPDATE example_table SET COLUMN_A = 1 WHERE primary_k...
I have a very large table that I need to iterate through with a PHP script and I can't do all of the results at once so I do it in sections with a LIMIT like for ($x = 0; $x < 10000000; $x += 1...
So I had a table with a primary key and a bunch of different columns. Columns A, B, and C were all unsigned ints (like the primary key column) and each column had a unique constraint I dropped the...
I have tables A and B and then I have a many to many join table with foreign keys to both called a_b. Neither foreign key can be null and the combinations for the foreign keys to A and B are unique...
I need to drop all of the stored procedures from my MySQL database before I recreate them. How can I do so?
Currently, we have a CRUD plus reporting application that talks to one MySQL database. Intermittently users will report locks when searching, currently, I can only get the approximate time of when ...
Almost every table in my DB has triggers that fire on INSERT, UPDATE, DELETE and write the changes to a separate read only DB. This makes it possible to track changes and undo things well after the...
I am considering either removing some columns or changing the datatypes if I could significantly reduce the amount of storage that is currently used by those columns. Some of the columns are ints a...
I have a database with quite a few VARCHAR fields. When the database was first built the lengths of the columns were set a bit larger than absolutely necessary. Now after, having used the DB for a ...
I have two tables with millions of records. Every so often I need to join them and exclude just a handful of records where a bit(1) column is set to 1 instead of 0. I can do it with either, WHERE ...
In programming instead of arrowcode where one has many layers of indented if statements, you can return a result as soon as possible. So instead of, if if end if end if It looks like if ret...
I have a number of MySQL stored procedures that use a cursor to go through a select and then pass the results to other stored procedures one row at a time. This can take a while to run, what is hap...
From time to time I will have large structural changes to make on my MySQL DB, things like adding columns, changing datatypes, adding indexes etc. These types of changes result in downtime and what...
I have a bunch of stored procedures that look like something this CREATE PROCEDURE example() BEGIN UPDATE STATEMENT A; UPDATE STATEMENT B; UPDATE STATEMENT C; END// When I run them thr...
If one finds where the past number of months equals the past number of days like this, select distinct DATE_SUB(now(), INTERVAL 92 DAY),DATE_SUB(now(), INTERVAL 3 MONTH) The numbers that are curre...
I need to add one column with the same name to all of the tables in my database, how can I find which tables don't currently have a column with that name?
Sometimes I will need to temporarily lock out other MySQL users when I am making large structure changes and want to make sure that nobody else is inputting or changing the data. The other use case...
I need to rename one column in 170 tables in a MySQL database and its going really slow. The columns all have an index plus a foreign key on them, would dropping the index/temporarily removing the...
