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I want to create a table in MySQL by running following SQL,
CREATE TABLE IF NOT EXISTS `shrewd_db`.`alert_disable_register` (
`id_alert_disable_register` MEDIUMINT NOT NULL AUTO_INCREMENT,
`id_label` MEDIUMINT UNSIGNED NULL,
`id_indicator` MEDIUMINT UNSIGNED NULL,
`id_user` MEDIUMINT UNSIGNED NULL,
`active` TINYINT(1) NULL DEFAULT 1,
`id_alert_disable_rule` MEDIUMINT NULL,
`id_escalation_plan` INT NULL,
PRIMARY KEY (`id_alert_disable_register`),
INDEX `id_escalation_plan_alert_rule_idx` (`id_alert_disable_rule` ASC),
INDEX `id_label_idx` (`id_label` ASC),
INDEX `id_indicator_idx` (`id_indicator` ASC),
INDEX `id_user_idx` (`id_user` ASC),
INDEX `id_escalation_plan_idx` (`id_escalation_plan` ASC),
CONSTRAINT `id_label`
FOREIGN KEY (`id_label`)
REFERENCES `shrewd_db`.`escalation_plan` (`id_label`)
ON DELETE NO ACTION
ON UPDATE NO ACTION,
CONSTRAINT `id_indicator`
FOREIGN KEY (`id_indicator`)
REFERENCES `shrewd_db`.`escalation_plan` (`id_indicator`)
ON DELETE NO ACTION
ON UPDATE NO ACTION,
CONSTRAINT `id_user`
FOREIGN KEY (`id_user`)
REFERENCES `shrewd_db`.`escalation_plan_task_group_has_user` (`id_user`)
ON DELETE NO ACTION
ON UPDATE NO ACTION,
CONSTRAINT `id_alert_disable_rule`
FOREIGN KEY (`id_alert_disable_rule`)
REFERENCES `shrewd_db`.`alert_disable_rule` (`id_alert_disable_rule`)
ON DELETE SET NULL
ON UPDATE SET NULL,
CONSTRAINT `id_escalation_plan`
FOREIGN KEY (`id_escalation_plan`)
REFERENCES `shrewd_db`.`escalation_plan` (`id_escalation_plan`)
ON DELETE NO ACTION
ON UPDATE NO ACTION)
ENGINE = InnoDB;
but I'm getting following error,
ERROR 1005 (HY000): Can't create table
'shrewd_db.alert_disable_register' (errno: 150)
Can anyone help me to resolve this, :)
Please find below create scripts of other required tables below,
CREATE TABLE `escalation_plan` (
`id_escalation_plan` int(10) unsigned NOT NULL AUTO_INCREMENT,
`id_indicator` mediumint(8) unsigned NOT NULL,
`id_label` mediumint(8) unsigned NOT NULL,
`pressure_waiting_hrs` int(11) NOT NULL DEFAULT '6',
PRIMARY KEY (`id_escalation_plan`),
KEY `fk_escalation_plan_escalation_plan1_idx` (`id_indicator`),
KEY `fk_escalation_plan_label1_idx` (`id_label`),
CONSTRAINT `fk_escalation_plan_escalation_plan1` FOREIGN KEY (`id_indicator`) REFERENCES `indicator` (`id_indicator`) ON DELETE NO ACTION ON UPDATE NO ACTION,
CONSTRAINT `fk_escalation_plan_label1` FOREIGN KEY (`id_label`) REFERENCES `label` (`id_label`) ON DELETE NO ACTION ON UPDATE NO ACTION
) ENGINE=InnoDB AUTO_INCREMENT=152 DEFAULT CHARSET=utf8;
CREATE TABLE `escalation_plan_task_group_has_user` (
`id_escalation_plan_task_has_user` int(10) unsigned NOT NULL AUTO_INCREMENT,
`id_user` mediumint(8) unsigned NOT NULL,
`id_escalation_plan_task_group` int(11) NOT NULL,
`text_alert` tinyint(1) NOT NULL DEFAULT '1',
`email_alert` tinyint(1) NOT NULL DEFAULT '1',
PRIMARY KEY (`id_escalation_plan_task_has_user`),
KEY `fk_escalation_plan_task_has_user_user1_idx` (`id_user`),
KEY `fk_escalation_plan_task_group_has_user_escalation_plan_task_idx` (`id_escalation_plan_task_group`),
CONSTRAINT `fk_escalation_plan_task_group_has_user_escalation_plan_task_g1` FOREIGN KEY (`id_escalation_plan_task_group`) REFERENCES `escalation_plan_task_group` (`id_escalation_plan_task_group`) ON DELETE NO ACTION ON UPDATE NO ACTION,
CONSTRAINT `fk_escalation_plan_task_has_user_user1` FOREIGN KEY (`id_user`) REFERENCES `user` (`id_user`) ON DELETE NO ACTION ON UPDATE NO ACTION
) ENGINE=InnoDB AUTO_INCREMENT=3605 DEFAULT CHARSET=utf8;
CREATE TABLE `alert_disable_rule` (
`id_alert_disable_rule` mediumint(9) NOT NULL AUTO_INCREMENT,
`disable_in_weekend` tinyint(1) DEFAULT '0',
`start_date` datetime DEFAULT NULL,
`end_date` datetime DEFAULT NULL,
`start_time` decimal(10,0) DEFAULT NULL,
`end_time` decimal(10,0) DEFAULT NULL,
PRIMARY KEY (`id_alert_disable_rule`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
In order for Foreign Key constraints to succeed, the following must be met, among other things:
The datatype1 and sign must match
The referenced table must have a left-most2 index on the relevant column(s) for speedy constraint verification.
Collation can play a factor. Please see answer of mine.
In your case, the indexes were fine, but as Solarflare mentioned, it was only your datatypes here that mattered and were mis-matched:
`alert_disable_register`.`id_escalation_plan`-- signed int
`escalation_plan`.`id_escalation_plan` -- unsigned int
Note that the display width (your numbers in parentheses) and nullability do not matter.
From the Mysql Manual Page Using FOREIGN KEY Constraints:
Corresponding columns in the foreign key and the referenced key must
have similar data types. The size and sign of integer types must be
the same. The length of string types need not be the same. For
nonbinary (character) string columns, the character set and collation
must be the same.
MySQL requires indexes on foreign keys and referenced keys so that
foreign key checks can be fast and not require a table scan. In the
referencing table, there must be an index where the foreign key
columns are listed as the first columns in the same order.
Corresponding columns in the foreign key and the referenced key must
have similar data types. The size and sign of integer types must be
the same. The length of string types need not be the same. For
nonbinary (character) string columns, the character set and collation
must be the same.
Also note that the referenced table key to satisfy the FK relationship does not need to be a Primary Key or even a Unique key. Just first-most (also known left-most2) in ordering to satisfy.
Again, the indexes were not your issue, but it often is for others.
For those needing to add Foreign Key constraints after table creation, use the ALTER TABLE statement.
The following test will run fine. You will need to decide how you want to deal with your changes on your own though. You were missing some tables provided which required remming out some FK constraints in the top 2 tables.
create database xyztest123;
use xyztest123;
CREATE TABLE `escalation_plan` (
`id_escalation_plan` int(10) unsigned NOT NULL AUTO_INCREMENT,
`id_indicator` mediumint(8) unsigned NOT NULL,
`id_label` mediumint(8) unsigned NOT NULL,
`pressure_waiting_hrs` int(11) NOT NULL DEFAULT '6',
PRIMARY KEY (`id_escalation_plan`),
KEY `fk_escalation_plan_escalation_plan1_idx` (`id_indicator`),
KEY `fk_escalation_plan_label1_idx` (`id_label`)
-- CONSTRAINT `fk_escalation_plan_escalation_plan1` FOREIGN KEY (`id_indicator`) REFERENCES `indicator` (`id_indicator`) ON DELETE NO ACTION ON UPDATE NO ACTION,
-- CONSTRAINT `fk_escalation_plan_label1` FOREIGN KEY (`id_label`) REFERENCES `label` (`id_label`) ON DELETE NO ACTION ON UPDATE NO ACTION
) ENGINE=InnoDB AUTO_INCREMENT=152 DEFAULT CHARSET=utf8;
CREATE TABLE `escalation_plan_task_group_has_user` (
`id_escalation_plan_task_has_user` int(10) unsigned NOT NULL AUTO_INCREMENT,
`id_user` mediumint(8) unsigned NOT NULL,
`id_escalation_plan_task_group` int(11) NOT NULL,
`text_alert` tinyint(1) NOT NULL DEFAULT '1',
`email_alert` tinyint(1) NOT NULL DEFAULT '1',
PRIMARY KEY (`id_escalation_plan_task_has_user`),
KEY `fk_escalation_plan_task_has_user_user1_idx` (`id_user`),
KEY `fk_escalation_plan_task_group_has_user_escalation_plan_task_idx` (`id_escalation_plan_task_group`)
-- CONSTRAINT `fk_escalation_plan_task_group_has_user_escalation_plan_task_g1` FOREIGN KEY (`id_escalation_plan_task_group`) REFERENCES `escalation_plan_task_group` (`id_escalation_plan_task_group`) ON DELETE NO ACTION ON UPDATE NO ACTION,
-- CONSTRAINT `fk_escalation_plan_task_has_user_user1` FOREIGN KEY (`id_user`) REFERENCES `user` (`id_user`) ON DELETE NO ACTION ON UPDATE NO ACTION
) ENGINE=InnoDB AUTO_INCREMENT=3605 DEFAULT CHARSET=utf8;
CREATE TABLE `alert_disable_rule` (
`id_alert_disable_rule` mediumint(9) NOT NULL AUTO_INCREMENT,
`disable_in_weekend` tinyint(1) DEFAULT '0',
`start_date` datetime DEFAULT NULL,
`end_date` datetime DEFAULT NULL,
`start_time` decimal(10,0) DEFAULT NULL,
`end_time` decimal(10,0) DEFAULT NULL,
PRIMARY KEY (`id_alert_disable_rule`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
CREATE TABLE IF NOT EXISTS `alert_disable_register` (
`id_alert_disable_register` MEDIUMINT NOT NULL AUTO_INCREMENT,
`id_label` MEDIUMINT UNSIGNED NULL,
`id_indicator` MEDIUMINT UNSIGNED NULL,
`id_user` MEDIUMINT UNSIGNED NULL,
`active` TINYINT(1) NULL DEFAULT 1,
`id_alert_disable_rule` MEDIUMINT NULL,
`id_escalation_plan` INT unsigned NULL,
PRIMARY KEY (`id_alert_disable_register`),
INDEX `id_escalation_plan_alert_rule_idx` (`id_alert_disable_rule` ASC),
INDEX `id_label_idx` (`id_label` ASC),
INDEX `id_indicator_idx` (`id_indicator` ASC),
INDEX `id_user_idx` (`id_user` ASC),
INDEX `id_escalation_plan_idx` (`id_escalation_plan` ASC),
CONSTRAINT `id_label`
FOREIGN KEY (`id_label`) -- MEDIUMINT UNSIGNED
REFERENCES `escalation_plan` (`id_label`) -- mediumint(8) unsigned , -- Index OK?: Yes
ON DELETE NO ACTION
ON UPDATE NO ACTION,
CONSTRAINT `id_indicator`
FOREIGN KEY (`id_indicator`) -- MEDIUMINT UNSIGNED
REFERENCES `escalation_plan` (`id_indicator`) -- mediumint(8) unsigned, -- Index OK?: Yes
ON DELETE NO ACTION
ON UPDATE NO ACTION,
CONSTRAINT `id_user`
FOREIGN KEY (`id_user`) -- MEDIUMINT UNSIGNED
REFERENCES `escalation_plan_task_group_has_user` (`id_user`) -- mediumint(8) unsigned, -- Index OK?: Yes
ON DELETE NO ACTION
ON UPDATE NO ACTION,
CONSTRAINT `id_alert_disable_rule`
FOREIGN KEY (`id_alert_disable_rule`) -- MEDIUMINT
REFERENCES `alert_disable_rule` (`id_alert_disable_rule`) -- mediumint(9), -- Index OK?: Yes
ON DELETE SET NULL
ON UPDATE SET NULL,
CONSTRAINT `id_escalation_plan`
FOREIGN KEY (`id_escalation_plan`) -- INT
REFERENCES `escalation_plan` (`id_escalation_plan`) -- int(10) unsigned, Index OK?: Yes
ON DELETE NO ACTION
ON UPDATE NO ACTION)
ENGINE = InnoDB;
drop database xyztest123;
1 Similar and allowable column differences, String data
drop table if exists a2; -- must do in reverse order
drop table if exists a1;
create table a1
( id int auto_increment primary key,
thing varchar(100) not null,
key `keyname001` (thing)
)ENGINE = InnoDB;
create table a2
( id int auto_increment primary key,
myThing char(40) not null, -- similar and allowable datatype
foreign key `fk_002` (myThing) references a1(thing)
)ENGINE = InnoDB;
insert a2(myThing) values ('a'); -- error 1452, FK violation
insert a1(thing) values ('a'); -- ok
insert a2(myThing) values ('a'); -- ok, not FK violation
-- now a redo below to show it slightly different
drop table if exists a2; -- must do in reverse order
drop table if exists a1;
create table a1
( id int auto_increment primary key,
thing varchar(100) not null,
key `keyname001` (thing)
)ENGINE = InnoDB;
create table a2
( id int auto_increment primary key,
myThing varchar(30) not null, -- similar and allowable datatype
key(myThing),
foreign key `fk_002` (myThing) references a1(thing)
)ENGINE = InnoDB;
insert a2(myThing) values ('a'); -- error 1452, FK violation
insert a1(thing) values ('a'); -- ok
insert a2(myThing) values ('a'); -- ok, not FK violation
2 Left-most / First-most index ordering
An index (a.k.a. a key) on a single column is left-most as it is not a composite index.
A multi-column index (a.k.a. a composite index) in a parent (a referenced) table is left-most satisfying if the ordering of its columns are in the same order as the child table key that depends on it for a foreign key (FK) relationship. Even if the count of columns in that parent composite key is greater than the count of the child composite key. See examples below.
Assuming a child (referencing) table has a composite key FK requirement ordering by (col1,col4) then
A parent composite key ordered by (col1,col2,col3,col4) does not satisfy the left-most requirement.
A parent composite key ordered by (col1,col4,col3, ...) does satisfy the left-most requirement.
The take-away here is that if such a parent key is not left-most satisfying, then the statement for the child table CREATE TABLE will fail for the FK relationship. The attempt to create the table will simply fail with an error code 1215.
Likewise, an ALTER TABLE for the child that exists will fail in an attempt to add an FK relationship after-the-fact.
I am having an issue with a MySQL database I'm working on. I have a table DAY_ITEM with two nullable columns, FOOD_ID and MEAL_ID, that are foreign keys to the ID column in FOOD_ITEM and MEAL_ITEM tables respectively.
When I try to insert a new record into the FOOD_ITEM table I get this error:
[HY000][1364] Field 'FOOD_ID' doesn't have a default value
But that column isn't in the FOOD_ITEM table, the FOOD_ITEM table only has the ID column which is the foreign key of the FOOD_ID column in the DAY_ITEM table.
Below are my SQL scripts that make the tables, what I am doing wrong in these scripts?
DAY_ITEM Script
CREATE TABLE DAY_ITEM
(
ID BIGINT NOT NULL,
EMAIL VARCHAR(50) NOT NULL,
NAME VARCHAR(100) NULL DEFAULT NULL,
MOD_ID SMALLINT NOT NULL, #MOD = Meal Of Day
MOD_NAME VARCHAR(50) NULL DEFAULT NULL,
DAYS_DATE DATE NOT NULL,
FOOD_ID BIGINT NULL DEFAULT NULL,
MEAL_ID BIGINT NULL DEFAULT NULL
);
ALTER TABLE DAY_ITEM
ADD CONSTRAINT DAY_ITEM_PK_ID
PRIMARY KEY (ID);
ALTER TABLE DAY_ITEM
MODIFY COLUMN ID BIGINT NOT NULL AUTO_INCREMENT;
ALTER TABLE DAY_ITEM
ADD CONSTRAINT DAY_ITEM_FK_EMAIL
FOREIGN KEY (EMAIL) REFERENCES USER_ACCOUNT (EMAIL);
ALTER TABLE DAY_ITEM
ADD CONSTRAINT DAY_ITEM_FK_FOOD_ID
FOREIGN KEY (FOOD_ID) REFERENCES FOOD_ITEM (ID);
ALTER TABLE DAY_ITEM
ADD CONSTRAINT DAY_ITEM_FK_MEAL_ID
FOREIGN KEY (MEAL_ID) REFERENCES MEAL_ITEM (ID);
ALTER TABLE DAY_ITEM
ADD CONSTRAINT MEAL_ITEM_UK_EMAIL_DAYSDATE_FOODID
UNIQUE (EMAIL, DAYS_DATE, MOD_ID, FOOD_ID);
ALTER TABLE DAY_ITEM
ADD CONSTRAINT MEAL_ITEM_UK_EMAIL_DAYSDATE_MEALID
UNIQUE (EMAIL, DAYS_DATE, MOD_ID, MEAL_ID);
FOOD_ITEM Script
CREATE TABLE FOOD_ITEM
(
ID BIGINT NOT NULL,
EMAIL VARCHAR(50) NOT NULL,
NAME VARCHAR(100) NULL DEFAULT NULL,
SERVING_AMOUNT DECIMAL(6, 2) NULL DEFAULT NULL,
SERVING_SIZE VARCHAR(50) NULL DEFAULT NULL,
SERVING_ID SMALLINT NOT NULL,
CALORIES SMALLINT NULL DEFAULT NULL,
PROTEIN SMALLINT NULL DEFAULT NULL,
CARBS SMALLINT NULL DEFAULT NULL,
SUGAR SMALLINT NULL DEFAULT NULL,
FIBER SMALLINT NULL DEFAULT NULL,
FAT SMALLINT NULL DEFAULT NULL,
SAT_FAT SMALLINT NULL DEFAULT NULL,
MONO_FAT SMALLINT NULL DEFAULT NULL,
POLY_FAT SMALLINT NULL DEFAULT NULL,
TRANS_FAT SMALLINT NULL DEFAULT NULL,
SODIUM BIGINT NULL DEFAULT NULL,
CHOLESTEROL BIGINT NULL DEFAULT NULL
);
ALTER TABLE FOOD_ITEM
ADD CONSTRAINT FOOD_ITEM_PK_ID
PRIMARY KEY (ID);
ALTER TABLE FOOD_ITEM
MODIFY COLUMN ID BIGINT NOT NULL AUTO_INCREMENT;
ALTER TABLE FOOD_ITEM
ADD CONSTRAINT FOOD_ITEM_FK_EMAIL
FOREIGN KEY (EMAIL) REFERENCES USER_ACCOUNT (EMAIL);
ALTER TABLE FOOD_ITEM
ADD CONSTRAINT FOOD_ITEM_UK_EMAIL_NAME_SERVING
UNIQUE (EMAIL, NAME, SERVING_AMOUNT, SERVING_SIZE, SERVING_ID);
EDIT
Here is the insert statement I'm using that throws the error:
INSERT INTO FOOD_ITEM (EMAIL, NAME, SERVING_AMOUNT, SERVING_SIZE, SERVING_ID, CALORIES, PROTEIN, CARBS, FAT)
VALUES ('userOne#gravytrack.com', 'Caviar 2', 1.00, 'serving', 0, 250, 12, 13, 14);
I don't see why it's looking at the FOOD_ID in DAY_ITEM at all. I'm not inserting into DAY_ITEM I'm inserting into FOOD_ITEM. Even though I don't include an ID here it should just auto-increment. That's the way it worked in the past before I added the DAY_ITEM table.
Try with removing Default NULL value and pass NULL while insert record.
your script shows like...
CREATE TABLE DAY_ITEM
(
ID BIGINT NOT NULL,
EMAIL VARCHAR(50) NOT NULL,
NAME VARCHAR(100) NULL DEFAULT NULL,
MOD_ID SMALLINT NOT NULL, #MOD = Meal Of Day
MOD_NAME VARCHAR(50) NULL DEFAULT NULL,
DAYS_DATE DATE NOT NULL,
FOOD_ID BIGINT NULL,
MEAL_ID BIGINT NULL
);
ALTER TABLE DAY_ITEM
ADD CONSTRAINT DAY_ITEM_PK_ID
PRIMARY KEY (ID);
ALTER TABLE DAY_ITEM
MODIFY COLUMN ID BIGINT NOT NULL AUTO_INCREMENT;
ALTER TABLE DAY_ITEM
ADD CONSTRAINT DAY_ITEM_FK_EMAIL
FOREIGN KEY (EMAIL) REFERENCES USER_ACCOUNT (EMAIL);
ALTER TABLE DAY_ITEM
ADD CONSTRAINT DAY_ITEM_FK_FOOD_ID
FOREIGN KEY (FOOD_ID) REFERENCES FOOD_ITEM (ID);
ALTER TABLE DAY_ITEM
ADD CONSTRAINT DAY_ITEM_FK_MEAL_ID
FOREIGN KEY (MEAL_ID) REFERENCES MEAL_ITEM (ID);
ALTER TABLE DAY_ITEM
ADD CONSTRAINT MEAL_ITEM_UK_EMAIL_DAYSDATE_FOODID
UNIQUE (EMAIL, DAYS_DATE, MOD_ID, FOOD_ID);
ALTER TABLE DAY_ITEM
ADD CONSTRAINT MEAL_ITEM_UK_EMAIL_DAYSDATE_MEALID
UNIQUE (EMAIL, DAYS_DATE, MOD_ID, MEAL_ID);
No need to change in second table.
insert a row with value NULL in id column in your parent table, then you can insert NULL value in child table.
Better option is you should avoid NULL values...
Update:
As you can see in your insert statement that food_id and meal_id fields are not included in insert statement means you are inserting default NULL value in these fields while in your master tables you have set these fields as not null means you are trying to insert a value (NULL) which does not exist in parent table.
am trying to implement a foreign key constraint but the mysql keeps giving me an error There are two tables "groups" table and "members" table.I have a many to many relationship between these tables and therefore used a third table called "members_groups" table for the many to many relationship. Note: "groups" and "members" tables have been created and contain data but I now want to add the "members_groups" table. Below are the sql codes:
Below is the script for the members table.
CREATE TABLE IF NOT EXISTS `members` (
`member_id` int(11) NOT NULL AUTO_INCREMENT,
`username` varchar(30) NOT NULL,
`email` varchar(50) NOT NULL,
`password` char(128) NOT NULL,
`salt` char(128) NOT NULL,
`group_id` bigint(64) unsigned NOT NULL,
`perm_override_add` bigint(64) unsigned NOT NULL,
`perm_override_remove` bigint(64) unsigned NOT NULL,
PRIMARY KEY (`member_id`),
KEY `member_id` (`member_id`)
) ENGINE=InnoDB;
script for the groups table
CREATE TABLE IF NOT EXISTS `groups` (
`group_id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`group_name` varchar(50) NOT NULL,
`permission` int(10) unsigned DEFAULT NULL,
PRIMARY KEY (`group_id`)
) ENGINE=InnoDB
script for the members_groups table
CREATE TABLE members_groups
(
member_id INT(11) NOT NULL ,
group_id INT(10) NOT NULL ,
PRIMARY KEY (member_id, group_id),
FOREIGN KEY (member_id) REFERENCES members(member_id) ON UPDATE CASCADE,
FOREIGN KEY (group_id) REFERENCES groups(group_id) ON UPDATE CASCADE
) ENGINE = InnoDB
This is the error I get from the mysql admin console.
Thanks.
You need to make the type same in your table. In your groups table you have defined
`group_id` int(10) unsigned NOT NULL AUTO_INCREMENT,
whereas in your members_groups table it is
group_id INT(10) NOT NULL ,
Try to make the change like
CREATE TABLE members_groups
(
member_id INT(11) NOT NULL ,
group_id INT(10) unsigned NOT NULL , --The datatype should be same as group_id in `groups` table
PRIMARY KEY (member_id, group_id),
FOREIGN KEY (member_id) REFERENCES members(member_id) ON UPDATE CASCADE,
FOREIGN KEY (group_id) REFERENCES `groups`(group_id) ON UPDATE CASCADE
) ENGINE = InnoDB;
SQL FIDDLE DEMO
Why this error occurs when pressing foreign key in the chat table?
create table user ( id int NOT NULL auto_increment,
userId int, username varchar(250),
useremail varchar(250),
primary key(id,userId));
CREATE table chat ( Id int NOT NULL auto_increment,
userId int, chatmsg varchar(250), time timestamp,
primary key(id),
foreign key (userId) references user (userId)
on update cascade on delete cascade);
There is no index on table user with leading column of userid. (That's why InnoDB is throwing an error on the FOREIGN KEY definition. InnoDB requires that there be a suitable index.)
If the tuple (id, userid) is defined as the PRIMARY KEY of the user table, the normative pattern would be for a foreign key reference to reference both of those columns.
But do you really need to have combination of the two columns as the PRIMARY KEY?
For example:
CREATE TABLE user
(
id INT NOT NULL AUTO_INCREMENT COMMENT 'pk',
username VARCHAR(250),
useremail VARCHAR(250),
PRIMARY KEY (id)
);
CREATE TABLE chat
(
id INT NOT NULL AUTO_INCREMENT COMMENT 'pk',
user_id INT COMMENT 'fk ref user(id)',
chatmsg VARCHAR(250),
time TIMESTAMP,
PRIMARY KEY (id),
CONSTRAINT FK_chat_user
FOREIGN KEY (user_id) REFERENCES user (id)
ON UPDATE CASCADE ON DELETE CASCADE
);
If you always want a row in chat associated with a user, then you can have the database enforce that by adding NOT NULL to the user_id column of chat.
Try out following queries to create table:
CREATE TABLE `user` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`userId` int(11) DEFAULT NULL,
`username` varchar(250) DEFAULT NULL,
`useremail` varchar(250) DEFAULT NULL,
PRIMARY KEY (`id`),
UNIQUE KEY `userId_UNIQUE` (`userId`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
CREATE TABLE `chat` (
`Id` int(11) NOT NULL AUTO_INCREMENT,
`userId` int(11) DEFAULT NULL,
`chatmsg` varchar(250) DEFAULT NULL,
`time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
PRIMARY KEY (`Id`),
KEY `fk_userid_idx` (`userId`),
CONSTRAINT `fk_userid` FOREIGN KEY (`userId`) REFERENCES `user` (`id`) ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
declare user table in this way
create table user (
id int NOT NULL auto_increment,
userId int,
username varchar(250),
useremail varchar(250),
primary key(id), key(userId)
);
I've created a table :
CREATE TABLE users (
id INT(6) UNSIGNED AUTO_INCREMENT PRIMARY KEY
,uName VARCHAR(50)
,uSecondName VARCHAR(50)
,eMail VARCHAR(50)
)
After this I even insert some data without any problems. But when I've tried to create new table with FOREIGN KEY referenced to users.id I've got an error:
CREATE TABLE posts(
id INT(6) AUTO_INCREMENT NOT NULL
,pTitle VARCHAR(155) NOT NULL DEFAULT 'not_set'
,pText TEXT
,pAuthor INT(6)
,PRIMARY KEY(id)
,CONSTRAINT fk_PerAuthor FOREIGN KEY (pAuthor)
REFERENCES users(id) ON DELETE CASCADE ON UPDATE CASCADE
);
Did I miss something?