Concurrency error when deleteing or updating multiple primary key fields


20-Feb-2018 12:01

concurrency error when deleteing or updating multiple primary key fields-83

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In the previous blog post you saw that there are three different approaches to representing an inheritance hierarchy and I explained Table per Hierarchy (TPH) as the default mapping strategy in EF Code First.

We argued that the disadvantages of TPH may be too serious for our design since it results in denormalized schemas that can become a major burden in the long run.

In the case of employees and store, you may have a circular dependency; in which all employees must be stationed at a store, so the employees table will have store ID and Employee ID attached as a concatonated primary key (Presuming that an Employee can only have one store stationed) or even just a simple non-dependent foriegn key.

Then each store must have a top general manager in charge which is stationed there, so the store will have an Employee ID Foreign Key to the store table to represent that the store has that employee as the manager.

/bin/sh# find-fk-conflicts.sh# (c) 2004 Turadg Aleahmad, licensed under GPL# USAGE: child_table child_key parent_table parent_key# NOTE: set thisdb="TARGET DATABASE"child_table=

In the previous blog post you saw that there are three different approaches to representing an inheritance hierarchy and I explained Table per Hierarchy (TPH) as the default mapping strategy in EF Code First.We argued that the disadvantages of TPH may be too serious for our design since it results in denormalized schemas that can become a major burden in the long run.In the case of employees and store, you may have a circular dependency; in which all employees must be stationed at a store, so the employees table will have store ID and Employee ID attached as a concatonated primary key (Presuming that an Employee can only have one store stationed) or even just a simple non-dependent foriegn key.Then each store must have a top general manager in charge which is stationed there, so the store will have an Employee ID Foreign Key to the store table to represent that the store has that employee as the manager.

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In the previous blog post you saw that there are three different approaches to representing an inheritance hierarchy and I explained Table per Hierarchy (TPH) as the default mapping strategy in EF Code First.

We argued that the disadvantages of TPH may be too serious for our design since it results in denormalized schemas that can become a major burden in the long run.

In the case of employees and store, you may have a circular dependency; in which all employees must be stationed at a store, so the employees table will have store ID and Employee ID attached as a concatonated primary key (Presuming that an Employee can only have one store stationed) or even just a simple non-dependent foriegn key.

Then each store must have a top general manager in charge which is stationed there, so the store will have an Employee ID Foreign Key to the store table to represent that the store has that employee as the manager.

/bin/sh# find-fk-conflicts.sh# (c) 2004 Turadg Aleahmad, licensed under GPL# USAGE: child_table child_key parent_table parent_key# NOTE: set thisdb="TARGET DATABASE"child_table=$1child_key=$2parent_table=$3parent_key=$4query="SELECT $child_table.$child_key FROM $child_table LEFT JOIN $parent_table ON ( $child_table.$child_key = $parent_table.$parent_key)WHERE $child_table.$child_key IS NOT NULL AND $parent_table.$parent_key IS NULL;"mysql --verbose -u root -e "$query" $db If you have a join on part of a primary key, foriegn key constraints may behave in an unexpected way.

CREATE TABLE doc (doc ID INTEGER NOT NULL AUTO_INCREMENT,lang Code CHAR(2) NOT NULL,title VARCHAR(32), PRIMARY KEY (doc ID, lang Code)) Type=Inno DB; CREATE TABLE author (author ID INTEGER NOT NULL AUTO_INCREMENT,doc ID CHAR(2) NOT NULL,name VARCHAR(32), PRIMARY KEY (author ID), FOREIGN KEY (doc ID) REFERENCES doc(doc ID) ON DELETE CASCADE ON UPDATE CASCADE) Type=Inno DB; In this case you have documents in several languages.

child_key=parent_table=parent_key=query="SELECT $child_table.$child_key FROM $child_table LEFT JOIN $parent_table ON ( $child_table.$child_key = $parent_table.$parent_key)WHERE $child_table.$child_key IS NOT NULL AND $parent_table.$parent_key IS NULL;"mysql --verbose -u root -e "$query" $db If you have a join on part of a primary key, foriegn key constraints may behave in an unexpected way.

CREATE TABLE doc (doc ID INTEGER NOT NULL AUTO_INCREMENT,lang Code CHAR(2) NOT NULL,title VARCHAR(32), PRIMARY KEY (doc ID, lang Code)) Type=Inno DB; CREATE TABLE author (author ID INTEGER NOT NULL AUTO_INCREMENT,doc ID CHAR(2) NOT NULL,name VARCHAR(32), PRIMARY KEY (author ID), FOREIGN KEY (doc ID) REFERENCES doc(doc ID) ON DELETE CASCADE ON UPDATE CASCADE) Type=Inno DB; In this case you have documents in several languages.

concurrency error when deleteing or updating multiple primary key fields-44

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For example: DELETE FROM doc WHERE docid=1 AND lang Code=en;now the tables look like:doc tabledoc ID lang Code title1 hu A Szamitogepauthor tableauthor ID doc ID name As you can see, deleting just the translation has deleted the author.So far, the strategies we’ve discussed require extra consideration with regard to the SQL schema (e.g. This situation changes with the Table per Concrete Type (TPC) that we will discuss in the next post.PDF (US Ltr) - 38.2Mb PDF (A4) - 38.2Mb PDF (RPM) - 37.1Mb HTML Download (TGZ) - 10.2Mb HTML Download (Zip) - 10.3Mb HTML Download (RPM) - 9.0Mb Man Pages (TGZ) - 206.2Kb Man Pages (Zip) - 314.7Kb Info (Gzip) - 3.5Mb Info (Zip) - 3.5Mb My SQL Backup and Recovery My SQL Globalization My SQL Information Schema My SQL Installation Guide My SQL and Linux/Unix My SQL and OS X My SQL Partitioning My SQL Performance Schema My SQL Replication Using the My SQL Yum Repository My SQL Restrictions and Limitations Security in My SQL My SQL and Solaris Building My SQL from Source Starting and Stopping My SQL My SQL Tutorial My SQL and Windows My SQL NDB Cluster 7.5 My SQL 5.7 Secure Deployment Guide PDF (US Ltr) - 38.2Mb PDF (A4) - 38.2Mb PDF (RPM) - 37.1Mb HTML Download (TGZ) - 10.2Mb HTML Download (Zip) - 10.3Mb HTML Download (RPM) - 9.0Mb Man Pages (TGZ) - 206.2Kb Man Pages (Zip) - 314.7Kb Info (Gzip) - 3.5Mb Info (Zip) - 3.5Mb My SQL Backup and Recovery My SQL Globalization My SQL Information Schema My SQL Installation Guide My SQL and Linux/Unix My SQL and OS X My SQL Partitioning My SQL Performance Schema My SQL Replication Using the My SQL Yum Repository My SQL Restrictions and Limitations Security in My SQL My SQL and Solaris Building My SQL from Source Starting and Stopping My SQL My SQL Tutorial My SQL and Windows My SQL NDB Cluster 7.5 My SQL 5.7 Secure Deployment Guide For those encountering the problem " ERROR 1216: Cannot add or update a child row: a foreign key constraint fails", it actually means what it says!Integrity constraint definition are also straightforward (note how Card Type in Credit Cards table is now a non-nullable column).



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