How to get column description using PDO? AS far as i understood fetchColumn and getColumnMeta does not return description field, which is part of MySQL database table.
I would like to write code as general as possible, thus i use PDO, which connects to all possible databases. Most probably description field is not available in all databases, thus there is no general function for retrieving it?
You can try :
$table_fields = $dbh->query("DESCRIBE tablename")->fetchAll();
It will return you all the column names of the table .
Or if you want it MySQL's side, you can try :
SHOW COLUMNS FROM <table_name> WHERE Field = ?
+-------+---------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------+---------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
+-------+---------+------+-----+---------+----------------+
Related
I'm using Mysql 5.5 and by example I have a table like this
+------------+-------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+------------+-------------+------+-----+---------+----------------+
| idgroups | int(11) | NO | PRI | NULL | auto_increment |
| group_id | int(11) | YES | | NULL | |
| group_name | varchar(45) | YES | | NULL |
Where some people are allowed to do inserts,update and delete but I want to know which is the last modified row or row's id in a given time
Any ideas?
Thanks in advance
My suggestion would be to create a second table. something like edit_history for recording modifications. You can put triggers on your groups table above that says "Any time a record is inserted, deleted, or updated, create a record in my edit_history table".
A trigger can be created as follows:
CREATE TRIGGER trigger_name
AFTER INSERT
ON table_name FOR EACH ROW
BEGIN
-- For each row inserted
-- do something...
END;
Since your field is auto_increment, you can just select the maximum value of idgroups to get the most recently inserted value:
select max(idgroups) from tbl
to get last modified in general will require additional structure to your table. In particular, if you are deleting, you will need to store what you have most recently deleted somewhere.
I'm not talking about unique keys or auto_increments, suppose I have this structure:
mysql> describe email_notifications;
+---------------+------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+---------------+------------------+------+-----+---------+----------------+
| email_id | int(11) unsigned | NO | PRI | NULL | auto_increment |
| email_address | varchar(100) | NO | | | |
| course_id | int(11) unsigned | NO | MUL | NULL | |
+---------------+------------------+------+-----+---------+----------------+
I'm building (for fun, practice, and hopefully some practical use) a tool in PHP that will analyze the structure of each table in a database and then compare it to a newer one (to assist in Dev -> Live updates), and then spit out some MySQL queries (Such as ALTER TABLE...) that I can run on the live database in order to bring it up to speed.
The question - does each field get a unique id of some sort?
If I change email_address from varchar(100) to text (for example) or the name course_id to cr_id, is there any way for me to tell that it's still technically the same dataset? I don't want to run a Delete and Add, but instead rename it give it a new type.
Or if there's a better way to do it without some sort of MySQL ID, that would be great :)
Thanks!
I think you can use information_schema.columns. The following are both unique keys in this table (even if they are not so defined):
TABLE_CATALOG, TABLE_SCHEMA, TABLE_NAME, COLUMN_NAME
TABLE_CATALOG, TABLE_SCHEMA, TABLE_NAME, ORDINAL_POSITION
When you change the name or type of a column, I do not believe that ORDINAL_POSITION is affected. So, the second version may be what you are looking for.
This may then lead to the question "what if I change the name of a table?" The information_schema tables can't help there, unfortunately.
We are implementing a system that analyses books. The system is written in PHP, and for each book loops through the words and analyses each of them, setting certain flags (that translate to database fields) from various regular expressions and other tests.
This results in a matches table, similar to the example below:
+------------------------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+------------------------+--------------+------+-----+---------+----------------+
| id | bigint(20) | NO | PRI | NULL | auto_increment |
| regex | varchar(250) | YES | | NULL | |
| description | varchar(250) | NO | | NULL | |
| phonic_description | varchar(255) | NO | | NULL | |
| is_high_frequency | tinyint(1) | NO | | NULL | |
| is_readable | tinyint(1) | NO | | NULL | |
| book_id | bigint(20) | YES | | NULL | |
| matched_regex | varchar(255) | YES | | NULL | |
| [...] | | | | | |
+------------------------+--------------+------+-----+---------+----------------+
Most of the omitted fields are tinyint, either 0 or 1. There are currently 25 fields in the matches table.
There are ~2,000,000 rows in the matches table, the output of analyzing ~500 books.
Currently, there is a "reports" area of the site which queries the matches table like this:
SELECT COUNT(*)
FROM matches
WHERE is_readable = 1
AND other_flag = 0
AND another_flag = 1
However, at present it takes over a minute to fetch the main index report as each query takes about 0.7 seconds. I am caching this at a query level, but it still takes too long for the initial page load.
As I am not very experienced in how to manage datasets such as this, can anyone advise me of a better way to store or query this data? Are there any optimisations I can use with MySQL to improve the performance of these COUNTs, or am I better off using another database or data structure?
We are currently using MySQL with MyISAM tables and a VPS for this, so switching to a new database system altogether isn't out of the question.
You need to use indexes, create them on the columns you do a WHERE on most frequently.
ALTER TABLE `matches` ADD INDEX ( `is_readable` )
etc..
You can also create indexes based on multiple columns, if your doing the same type of query over and over its useful. phpMyAdmin has the index option on the structure page of the table at the bottom.
Add multi index to this table as you are selecting by more than one field. Below index should help a lot. Those type of indexes are very good for boolean / int columns. For indexes with varchar values read more here: http://dev.mysql.com/doc/refman/5.0/en/create-index.html
ALTER TABLE `matches` ADD INDEX ( `is_readable`, `other_flag`, `another_flag` )
One more thing is to check your queries by using EXPLAIN {YOUR WHOLE SQL STATEMENT} to check which index is used by DB. So in this example you should run query:
EXPLAIN ALTER TABLE `matches` ADD INDEX ( `is_readable`, `other_flag`, `another_flag` )
More info on EXPLAIN: http://dev.mysql.com/doc/refman/5.0/en/explain.html
I've made a table:
+---------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+---------+--------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| date | date | NO | | NULL | |
| user_id | int(8) | YES | | NULL | |
| isbn | varchar(13) | NO | | NULL | |
| price | decimal(6,2) | NO | | NULL | |
+---------+--------------+------+-----+---------+----------------+
And, the date colomn isn't working. I figured I need to modify the table to default to "CURDATE()". That's what I've got from googling. I'm not even sure if that's the problem, but my alter statement isn't work.
I'm trying to alter with this:
mysql> ALTER TABLE buybacks MODIFY date date not null default curdate();
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'curdate()' at line 1
Can someone help?
It's generally not a good idea to have column (or table) names that are MySQL reserved words. If you must do this, then use backticks (`) around the name
ALTER TABLE buybacks MODIFY `date` date not null default curdate();
EDIT
However, you can't set a date column to a default of curdate()
See this reference from the MySQL buglist for details
The exception is that you can specify CURRENT_TIMESTAMP as the default for a TIMESTAMP
column. This might be a viable alternative to give you that default
EDIT 2
Another alternative would be a trigger:
CREATE TRIGGER buybacks_insert BEFORE INSERT ON `buybacks`
FOR EACH ROW
SET NEW.`date` = CURDATE();
But watch out that you update a trigger when you do change the name of the date column
i develop a project, in that i display the values from mysql database using PHP , in that i need to set a unique id[Not manually] for each row that i fetched from database.Can anyone help me please. Thanks in Advance.
Take a look at this article for how to create an auto incremented field to generate unique ID for the record:
http://www.plus2net.com/sql_tutorial/mysql_auto_increment.php
Basicly you use AUTO_INCREMENT attribute on the column.
This
CREATE TABLE animals (
id MEDIUMINT NOT NULL AUTO_INCREMENT,
name CHAR(30) NOT NULL,
PRIMARY KEY (id)
);
INSERT INTO animals (name) VALUES
('dog'),('cat'),('penguin'),
('lax'),('whale'),('ostrich');
SELECT * FROM animals;
Will create this output:
+----+---------+
| id | name |
+----+---------+
| 1 | dog |
| 2 | cat |
| 3 | penguin |
| 4 | lax |
| 5 | whale |
| 6 | ostrich |
+----+---------+
How to automatically generate ids has already been answered. Additional info: If you want to see which id was inserted for a row, use mysql_insert_id()
Alternatively, you should already have a primary key or compound key, get a hash of these using the md5 function and store in memory. However, creating an auto incrementing field or a UUID field in the database would be the most preferable option.
HI, Even i have come across the same situation, where I need to display the row id. To implement this, i have created a separated table, where I Control the table with Stored Procedure, before it refills, I will delete all the records and reinserts with the latest Ranking systems. I am successful in this and implemented in
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