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Q&A

Posts tagged mysql

Subtag of sql

Use this tag for questions about MySQL database system. MySQL is a free, open source Relational Database Management System that uses SQL. This tag should not be used for questions dealing with other SQL dialects such as SQLite, SQL Server (T-SQL).

This tag doesn't have a detailed wiki yet.

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Q&A Why OFFSET isn't working the way it is expected?

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'...

1 answer  ·  posted 3mo ago by billy‭  ·  edited 3mo ago by Alexei‭

Question mysql sql
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Q&A Conditions which always matches returns no result with CTE

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...

1 answer  ·  posted 11mo ago by artaxerxe‭  ·  edited 11mo ago by Alexei‭

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Q&A Is an ORDER BY required when looping through MySQL records with LIMIT?

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...

1 answer  ·  posted 2y ago by Charlie Brumbaugh‭  ·  edited 12mo ago by Alexei‭

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Q&A How to to make a store tree view cart

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...

0 answers  ·  posted 1y ago by Fyoni‭  ·  edited 1y ago by Alexei‭

Question php mysql pdo treeview
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Q&A How to create a MySQL generated column that uses a join in a concat?

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...

1 answer  ·  posted 1y ago by Charlie Brumbaugh‭  ·  last activity 1y ago by Alexei‭

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Q&A How to start mysql in Manjaro from terminal?

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...

1 answer  ·  posted 1y ago by deleted user  ·  last activity 1y ago by deleted user

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Q&A When is information schema not needed and when is it indeed when migrating from one website hosting provider to another?

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...

0 answers  ·  posted 1y ago by deleted user  ·  edited 1y ago by deleted user

Question mysql database
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Q&A Is it possible to disable the "mysql: [Warning] Using a password on the command line interface can be insecure" warning?

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 ...

1 answer  ·  posted 2y ago by Charlie Brumbaugh‭  ·  last activity 2y ago by Alexei‭

Question mysql
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Q&A Is it unsecure to use a password on the command line to run a MySQL script on Windows?

Its possible to execute a MySQL file from the command line like so, mysql -u USER -pPASSWORD &lt; FILENAME which triggers a warning, mysql: [Warning] Using a password on the command line int...

2 answers  ·  posted 2y ago by Charlie Brumbaugh‭  ·  edited 2y ago by ghost-in-the-zsh‭

Question mysql windows
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Q&A How much memory is allocated for a MySQL VARCHAR variable in a stored procedure?

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...

2 answers  ·  posted 2y ago by Charlie Brumbaugh‭  ·  last activity 2y ago by Alexei‭

86%
+11 −0
Q&A Are there best practices for sticking conditions in WHERE clauses vs the JOIN statement?

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....

2 answers  ·  posted 2y ago by Charlie Brumbaugh‭  ·  last activity 2y ago by klutt‭

Question mysql join
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Q&A Is there a way to automatically fix MySQL tables where the auto_increment has fallen behind the correct value?

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...

1 answer  ·  posted 2y ago by Charlie Brumbaugh‭  ·  last activity 2y ago by Alexei‭

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Q&A In MySQL is there a limit to the number of keys in a IN() clause?

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...

2 answers  ·  posted 2y ago by Charlie Brumbaugh‭  ·  last activity 2y ago by Alexei‭

Question mysql
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Q&A Iterating through a MySQL table with a LIMIT clause and PHP gets progressively slower

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 &lt; 10000000; $x += 1...

1 answer  ·  posted 2y ago by Charlie Brumbaugh‭  ·  last activity 2y ago by ArtOfCode‭

Question php mysql
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Q&A Why would an unique index get moved to the primary key after the underlying column is dropped?

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...

1 answer  ·  posted 2y ago by Charlie Brumbaugh‭  ·  edited 2y ago by Alexei‭

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Q&A Is it possible in MySQL to require each row in a table have at least one foreign key record in a join table?

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...

2 answers  ·  posted 2y ago by Charlie Brumbaugh‭  ·  last activity 2y ago by Alexei‭

Question mysql referential
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Q&A How to drop all stored procedures from a MySQL database

I need to drop all of the stored procedures from my MySQL database before I recreate them. How can I do so?

1 answer  ·  posted 2y ago by Charlie Brumbaugh‭  ·  edited 2y ago by Peter Mortensen‭

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Q&A How do I track down intermittent locks in a MySQL database?

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 ...

0 answers  ·  posted 2y ago by Charlie Brumbaugh‭  ·  edited 2y ago by Alexei‭

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Q&A In MySQL, is it possible to disable triggers for only certain queries or users?

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...

1 answer  ·  posted 2y ago by Charlie Brumbaugh‭  ·  edited 2y ago by Alexei‭

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Q&A How to calculate how much data is stored in a MySQL column?

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...

1 answer  ·  posted 2y ago by Charlie Brumbaugh‭  ·  last activity 2y ago by Alexei‭

Question mysql
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Q&A Would a MySQL database run more efficiently with smaller varchar lengths?

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 ...

3 answers  ·  posted 2y ago by Charlie Brumbaugh‭  ·  last activity 2y ago by manassehkatz‭

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Q&A Why would excluding records by creating a temporary table of their primary keys be faster than simply excluding by value?

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 ...

2 answers  ·  posted 2y ago by Charlie Brumbaugh‭  ·  edited 2y ago by Alexei‭

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Q&A Is there an equivalent way of returning early in a MySQL stored procedure?

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...

1 answer  ·  posted 2y ago by Charlie Brumbaugh‭  ·  edited 2y ago by Moshi‭

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Q&A What is happening under the hood to the selected data in a MySQL cursor?

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...

0 answers  ·  posted 2y ago by Charlie Brumbaugh‭  ·  edited 2y ago by Charlie Brumbaugh‭

Question mysql
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Q&A Is there a way to estimate the execution time of a statement in MySQL?

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...

1 answer  ·  posted 2y ago by Charlie Brumbaugh‭  ·  last activity 2y ago by meriton‭

Question mysql
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Q&A In a stored procedure, is it possible to get the total number or rows updated by different statements?

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...

2 answers  ·  posted 2y ago by Charlie Brumbaugh‭  ·  last activity 2y ago by Alexei‭

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Q&A How long in days is a MONTH in MySQL?

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...

1 answer  ·  posted 2y ago by Charlie Brumbaugh‭  ·  last activity 2y ago by r~~‭

Question mysql
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Q&A How do I find all the tables in a database that don't have a specific column?

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?

1 answer  ·  posted 2y ago by Charlie Brumbaugh‭  ·  last activity 2y ago by Charlie Brumbaugh‭

Question mysql
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Q&A How to temporarily disable a MySQL user?

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...

2 answers  ·  posted 2y ago by Charlie Brumbaugh‭  ·  edited 2y ago by Charlie Brumbaugh‭

Question mysql
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Q&A Can renaming a MySQL column be sped up by dropping indexes or foreign keys?

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...

2 answers  ·  posted 2y ago by Charlie Brumbaugh‭  ·  last activity 2y ago by manassehkatz‭