MySQL Server Administration. Identifier Case Sensitivity. Mapping of Identifiers to File Names. Function Name Parsing and Resolution. The InnoDB Storage Engine. Using MySQL as a Document Store. InnoDB Cluster. InnoDB ReplicaSet. MySQL on the OCI Marketplace. Error Messages and Common Problems. MySQL 8. PDF US Ltr - version 8. Value Meaning 0 Table and database names are stored on disk using the lettercase specified in the CREATE TABLE or CREATE DATABASE statement.

Name comparisons are case-sensitive. You should not set this variable to 0 if you are running MySQL on a system that has case-insensitive file names such as Windows or macOS. MySQL converts all table names to lowercase on storage and lookup. This behavior also applies to database names and table aliases. Download multiple files at one time Download large files quickly and reliably Suspend active downloads and resume downloads that have failed. Yes, install Microsoft Download Manager recommended No, thanks.

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File Size:. System Requirements Supported Operating System. Install Instructions The download is a pdf file. There are two more databases created within each cluster during initialization, named template1 and template0. As the names suggest, these will be used as templates for subsequently-created databases; they should not be used for actual work.

See Chapter 23 for information about creating new databases within a cluster. In file system terms, a database cluster is a single directory under which all data will be stored. We call this the data directory or data area. It is completely up to you where you choose to store your data. The data directory must be initialized before being used, using the program initdb which is installed with PostgreSQL.

If you are using a pre-packaged version of PostgreSQL , it may well have a specific convention for where to place the data directory, and it may also provide a script for creating the data directory. In that case you should use that script in preference to running initdb directly.

Consult the package-level documentation for details. To initialize a database cluster manually, run initdb and specify the desired file system location of the database cluster with the -D option, for example:.

Note that you must execute this command while logged into the PostgreSQL user account, which is described in the previous section.

As an alternative to the -D option, you can set the environment variable PGDATA. initdb will attempt to create the directory you specify if it does not already exist.

Of course, this will fail if initdb does not have permissions to write in the parent directory. It's generally recommendable that the PostgreSQL user own not just the data directory but its parent directory as well, so that this should not be a problem. If the desired parent directory doesn't exist either, you will need to create it first, using root privileges if the grandparent directory isn't writable.

So the process might look like this:. initdb will refuse to run if the data directory exists and already contains files; this is to prevent accidentally overwriting an existing installation. Because the data directory contains all the data stored in the database, it is essential that it be secured from unauthorized access.

initdb therefore revokes access permissions from everyone but the PostgreSQL user, and optionally, group.

Group access, when enabled, is read-only. This allows an unprivileged user in the same group as the cluster owner to take a backup of the cluster data or perform other operations that only require read access. Note that enabling or disabling group access on an existing cluster requires the cluster to be shut down and the appropriate mode to be set on all directories and files before restarting PostgreSQL.

Otherwise, a mix of modes might exist in the data directory. For clusters that allow access only by the owner, the appropriate modes are for directories and for files. For clusters that also allow reads by the group, the appropriate modes are for directories and for files.

In MySQL, databases correspond to directories within the data directory. Each table within a database corresponds to at least one file within the database directory and possibly more, depending on the storage engine. Triggers also correspond to files. Consequently, the case sensitivity of the underlying operating system plays a part in the case sensitivity of database, table, and trigger names. This means such names are not case-sensitive in Windows, but are case-sensitive in most varieties of Unix.

However, macOS also supports UFS volumes, which are case-sensitive just as on any Unix. See Section 1. Although database, table, and trigger names are not case-sensitive on some platforms, you should not refer to one of these using different cases within the same statement. Partition, subpartition, column, index, stored routine, event, and resource group names are not case-sensitive on any platform, nor are column aliases.

However, names of logfile groups are case-sensitive. This differs from standard SQL. By default, table aliases are case-sensitive on Unix, but not so on Windows or macOS. The following statement would not work on Unix, because it refers to the alias both as a and as A :. However, this same statement is permitted on Windows. To avoid problems caused by such differences, it is best to adopt a consistent convention, such as always creating and referring to databases and tables using lowercase names.

This convention is recommended for maximum portability and ease of use. This variable does not affect case sensitivity of trigger identifiers. On Windows, the default value is 1.

On macOS, the default value is 2. However, you may encounter difficulties if you want to transfer tables between platforms that differ in file system case sensitivity. To avoid data transfer problems arising from lettercase of database or table names, you have two options:. The main disadvantage with this is that when you use SHOW TABLES or SHOW DATABASES , you do not see the names in their original lettercase.

This preserves the lettercase of database and table names. The disadvantage of this is that you must ensure that your statements always refer to your database and table names with the correct lettercase on Windows. If you transfer your statements to Unix, where lettercase is significant, they do not work if the lettercase is incorrect. Object names may be considered duplicates if their uppercase forms are equal according to a binary collation.

That is true for names of cursors, conditions, procedures, functions, savepoints, stored routine parameters, stored program local variables, and plugins. It is not true for names of columns, constraints, databases, partitions, statements prepared with PREPARE , tables, triggers, users, and user-defined variables.

For more information, see Section Documentation Home MySQL 8. MySQL Server Administration. Identifier Case Sensitivity. Mapping of Identifiers to File Names. Function Name Parsing and Resolution. The InnoDB Storage Engine. Using MySQL as a Document Store. InnoDB Cluster. InnoDB ReplicaSet. MySQL on the OCI Marketplace. Error Messages and Common Problems.

MySQL 8. PDF US Ltr - version 8. Value Meaning 0 Table and database names are stored on disk using the lettercase specified in the CREATE TABLE or CREATE DATABASE statement. Name comparisons are case-sensitive. You should not set this variable to 0 if you are running MySQL on a system that has case-insensitive file names such as Windows or macOS. MySQL converts all table names to lowercase on storage and lookup.

This behavior also applies to database names and table aliases. Name comparisons are not case-sensitive. This works only on file systems that are not case-sensitive! PREV HOME UP NEXT. Related Documentation MySQL 8. Table and database names are stored on disk using the lettercase specified in the CREATE TABLE or CREATE DATABASE statement. Table names are stored in lowercase on disk and name comparisons are not case-sensitive.

Table and database names are stored on disk using the lettercase specified in the CREATE TABLE or CREATE DATABASE statement, but MySQL converts them to lowercase on lookup.

Creating Spatial Indexes. It can be temporary or dismissable. Include large objects in the dump. This option is useful when needing to synchronize the dump with a logical replication slot see Chapter 49 or with a concurrent session. You should not set this variable to 0 if you are running MySQL on a system that has case-insensitive file names such as Windows or macOS. If --clean is also specified, the script drops and recreates the target database before reconnecting to it. Function Name Parsing and Resolution.

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