Migrating from Oracle to MySQL. VARCHAR2 length defined using bytes. How to port?

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I have variable in Oracle procedure declared like this:

myMsg  VARCHAR2(256 BYTE)

How can I port it to mysql? Because this when I try to declare it in MySQL procedure:

DECLARE myMsg VARCHAR(256 BYTE);

MySQL throws me syntax error.


How can I port that Oracle variable definition to MySQL?


It is 256 BYTE part that doesn't let me to declare variable in MySQL and I need to find something similar to this 256 BYTE expression in MySQL.

In MySql, varchar colums get declared like this

   colname VARCHAR(256),
   another VARCHAR(20) NOT NULL,

etcetera. The Oracle syntax is different.

In stored code in MySql, inside function or procedure scope, variables get declared like this:

    DECLARE myMsg VARCHAR(256);

If you're not aware of this, you soon will be: Oracle PL/SQL and MySql's little language for stored code are very different from each other.

Oracle and MySQL Compared, MySQL uses a set of grant tables to keep track of users and the privileges that they can have. The schema contains the definitions of the tables, views, indexes, users, In Oracle, the default length semantics is bytes for CHAR and VARCHAR2 When migrating MySQL databases to Oracle, SQL Developer maps each� etcetera. The Oracle syntax is different. In stored code in MySql, inside function or procedure scope, variables get declared like this: DECLARE myMsg VARCHAR(256); If you're not aware of this, you soon will be: Oracle PL/SQL and MySql's little language for stored code are very different from each other.

The maximum size of varchar in mysql is 255 before mysql 5.0.3

From MySql Doc:

A variable-length string. M represents the maximum column length in characters. In MySQL 5.0, the range of M is 0 to 255 before MySQL 5.0.3, and 0 to 65,535 in MySQL 5.0.3 and later

In MySQL 5.0.3 and later, a CHAR length greater than 255 is illegal and fails with an error

mysql> CREATE TABLE c1 (col1 INT, col2 CHAR(500));
ERROR 1074 (42000): Column length too big for column 'col' (max = 255);
**use BLOB or TEXT instead**

In the error its clearly mention that use BLOB or TEXT

For more info about string data type link

LENGTH - Get String Length, In Oracle, LENGTH function returns the length of a string in characters as In SQL Server, you can use LEN function, but note that it excludes trailing column, Oracle LENGTH returns the maximum length of the column (defined in Migration to MySQL Get Length in Bytes, LENGTHB function, DATALENGTH function� Migrating from Oracle RDBMS to MySQL/Percona Server is an enormous task. This blog offers a basic guide to migration, especially if you're coming from Oracle and have limited knowledge of MySQL. The blog does not offer a step-by-step process, but it provides general information of what you should consider before a migration from Oracle to MySQL/Percona Server.

This would be a VARBINARY(256) in MySQL.

Oracle to MySQL Migration, To migrate data and database schema from an Oracle database use SQLines Data tool. Try SQLines Online 34, VARCHAR2(n), Variable-length string, 1 ⇐ n ⇐ 4000, VARCHAR(n) MySQL. BYTE and CHAR column size semantics, Size is always in characters Converting user-defined functions from Oracle to MySQL:� The INSTR, LENGTH and SUBSTR functions always deal with characters, regardless of column definitions and the character sets. For times when you specifically need to deal in bytes Oracle provides the INSTRB, LENGTHB and SUBSTRB functions. Example The following examples use the LENGTH function using single- and multibyte database character set.

Migrating Oracle users to Cloud SQL for MySQL: Data types, users , Note that a MySQL 5.7 database has a limit of 65,535 bytes, for the entire row VARCHAR2(n) 11g MySQL does not allow users to create dedicated, defined types. To successfully migrate into Cloud SQL for MySQL database tables, converting Oracle tables into MySQL tables is a crucial stage with� Summary: in this tutorial, you will learn about the Oracle VARCHAR2 data type and how to use it to define variable-length character string columns. Introduction to Oracle VARCHAR2 data type. To store variable-length character strings, you use the Oracle VARCHAR2 data type. A VARCHAR2 column can store a value that ranges from 1 to 4000 bytes.

Extended Data Types in Oracle Database 12c , With the introduction of Extended Data Types, Oracle 12c optionally increases these maximum sizes. VARCHAR2 : 32767 bytes; NVARCHAR2 : 32767 bytes; RAW parameter value to EXTENDED allows for the new maximum lengths. instance affinity so that they DOC> can migrate across RAC nodes. If the databases are both using single byte character sets then there is no real difference between a column defined with BYTE as opposed to CHAR for it's length. The issue arises when you have one database using one language e.g. single byte character set and the other using a different language with multi-byte character set (e.g. UTF-8).

MySQL supports the CHAR and VARCHAR type for character type with a length that is less than 65,535 bytes. The CHAR type can have a maximum length of 255 bytes, and as of MySQL 3.23 it may also be declared with a length of 0 byte. Before MySQL 5.0.3, the length specification for the VARCHAR type is the same as the CHAR type.

Comments
  • Could you try DECLARE myMsg VARCHAR(256); ?
  • Yes, but will that mean the same?
  • I only know that VARCHAR(256) creates a variable for 256 characters (edited from comment belove), I'm not sure how to declare variables...
  • I'm sorry but your answer is not related to my question. And also, I'm using MysQL 5.0.3+
  • please see this answer
  • that variable declaration is inside the declared procedure. I just ommited this part, so that it would be easier to read. The question is really about how can I declare variable, like it was declare in oracle using this "256 BYTE" statement. I'm curious what does this statement mean. To my mind it declare varchar, which is 256 bytes long. So how can I do the same in MySQL?
  • i don't think mysql support anonymous code block/anonymous procedure like oracle plsql.