I have a field in a table that is of the text type, however it has the size of 8000 characters, in the Oracle database it gives the problem, I saw that if I switch to CLOB it works, however I am not getting using the syntax ALTER TABLE "table" MODIFY LOB ("column")
I need both the query for oracle and mysql, but I'm not finding a syntax from MODIFY text to CLOB to mysql
MySQL doesn't have a data type CLOB it has TEXT
Data Type
(CLOB)
TINYTEXT L + 1 bytes, where L < 2**8 (255)
TEXT L + 2 bytes, where L < 2**16 (64 K)
MEDIUMTEXT L + 3 bytes, where L < 2**24 (16 MB)
LONGTEXT L + 4 bytes, where L < 2**32 (4 GB)
You didn't find anything because they are called differently and are differently see size
so MySQL
ALTER TABLE `mytqable` MODIFY `colmunname` LONGTEXT
But oracle itself has the data type CLOB
alter table mytable modify (blob_column clob);
Related
I want to set the maximal size of a BLOB column to be up to 900KB.
Is there a way similar to the syntax of the other String Data types - for example
c CHAR(7),
vc VARCHAR(50),
pic BLOB (???)
to do this?
From the storage requirements section of the manual, the max size of the following fields:
TINYBLOB : L < 2^8 = 256 Bytes
BLOB : L < 2^16 = 65,536 Bytes
MEDIUMBLOB : L < 2^24 = 16,777,216 Bytes
LONGBLOB : L < 2^32 = 4,294,967,296 Bytes
In order to store 900KB, you would need to use a MEDIUMBLOB at the very minimum.
As far as I know, you can not specify your own size for the field.
With our IBM Database (AS400), it is possible to provide a size to a Blob field.
fieldName Blob(size in bytes)
The maximum Size is then visible like any other length
Screenshot from DBvisualizer:
Anybody knows how MySQL allocates disk space for fields like "TEXT" or "BLOB"
For example, what happens when I insert 10kb string into "TEXT" column? Is the entire 65kb data allocated or only 10kb?
This is explained in the documentation: http://dev.mysql.com/doc/refman/5.7/en/storage-requirements.html
BLOB, TEXT L + 2 bytes, where L < 2^16
MEDIUMBLOB, MEDIUMTEXT L + 3 bytes, where L < 2^24
LONGBLOB, LONGTEXT L + 4 bytes, where L < 2^32
Variable-length string types are stored using a length prefix plus
data. The length prefix requires from one to four bytes depending on
the data type, and the value of the prefix is L (the byte length of
the string). For example, storage for a MEDIUMTEXT value requires L
bytes to store the value plus three bytes to store the length of the
value.
So in short, the whole 65kb is not wasted.
I have a Table with 2 columns: 'Id' (datatype=INT) , 'Representation' (datatype=binary).
I want to store a hexadecimal value in the form of binary digits in the 'Representation' Column.
What is the Max number of Binary digits that i can store in the 'Representation' column ?
MySql
BINARY
The MySql docs on the binary data type, mention:
The permissible maximum length is the same for BINARY and VARBINARY as it is for CHAR and VARCHAR, except that the length for BINARY and VARBINARY is a length in bytes rather than in characters.
So binary is put on the same level as char, and varbinary as varchar.
The docs on the char data type, mention:
The length of a CHAR column is fixed to the length that you declare when you create the table. The length can be any value from 0 to 255.
So the maximum size for binary is therefore achieved with this:
CREATE TABLE mytable (
id int,
representation binary(255)
)
This corresponds to 255 bytes of data, which corresponds to 510 hexadecimal digits, or 2040 bits.
VARBINARY
The varbinary type can store up to 65,535 bytes, from which the sizes of the other columns must be subtracted. Again, this follows from the docs on varchar:
Values in VARCHAR columns are variable-length strings. The length can be specified as a value from 0 to 65,535. The effective maximum length of a VARCHAR is subject to the maximum row size (65,535 bytes, which is shared among all columns) and the character set used.
So let's say you would need room for about 500 bytes in other columns, then you could defined this table:
CREATE TABLE mytable (
id int, // takes 4 bytes
representation binary(65000),
// other fields come here, taking up less than 532 bytes
)
... you would have 65,000 bytes, i.e. 130,000 hexadecimal digits or 520,000 bits.
SQL Server Binary
The Transact-SQL docs on binary state:
binary [ ( n ) ]
Fixed-length binary data with a length of n bytes, where n is a value from 1 through 8,000. The storage size is n bytes.
This means that with this table definition:
CREATE TABLE mytable (
id int,
representation binary(8000)
)
... you can store 8,000 bytes, i.e. 16,000 hexadecimal digits or 64,000 bits.
Note that the limit for varbinary is the same. The following advise is given in the docs:
Use varbinary when the sizes of the column data entries vary considerably.
I understand that the maximum row limit in mysql is 65535, which is equal to (2 ^ 16) - 1. I also understand that it is bad database design to have extremely long rows like that. However, this is my schema
CREATE TABLE mytable(
a VARCHAR(20000),
b VARCHAR(20000),
c VARCHAR(20000),
d VARCHAR(5535)
) CHARACTER SET=latin1;
This is the output I get
Row size too large. The maximum row size for the used table type, not counting BLOBs, is 65535. This includes storage overhead, check the manual. You have to change some columns to TEXT or BLOBs
Let's do the math again
20000 + 20000 + 20000 + 5535 = 65535
which is equal to and does not surpass the limit. For the record, the highest value for column d that works is 5526.
I do not understand where those additional 9 characters come from.
The size of VARCHAR is calculated like this:
len + 1 bytes if column is 0 – 255 bytes, len + 2 bytes if column may require more than 255 bytes
so
CREATE TABLE mytable(
a VARCHAR(20000), -- 20002
b VARCHAR(20000), -- 20002
c VARCHAR(20000), -- 20002
d VARCHAR(5535) -- 5537
) CHARACTER SET=latin1;-- 65543 !!!! 8 Bytes to much
see this https://mariadb.com/kb/en/mariadb/data-type-storage-requirements/
from: http://dev.mysql.com/doc/refman/5.7/en/column-count-limit.html
row length = 1
+ (sum of column lengths)
+ (number of NULL columns + delete_flag + 7)/8
+ (number of variable-length columns)
Try change column type to VARCHAR (20000) NOT NULL
I am working on an app that allows people to upload data via pdf files. After reading the pdf with my app, i also like to store all characters in the pdf from the first page to the last page.
My fear is that a pdf file can be up to 80mb which can contain over 1 billion characters.
Can mysql handle such large amount of characters?
MySQL data storage requirements can be found here: MySQL5 storage requirements
There I find this table (L = length of string):
TINYBLOB, TINYTEXT L + 1 bytes, where L < 2^8 = 256b
BLOB, TEXT L + 2 bytes, where L < 2^16 = 65.536 = 65kb
MEDIUMBLOB, MEDIUMTEXT L + 3 bytes, where L < 2^24 = 16.777.216 = 16mb
LONGBLOB, LONGTEXT L + 4 bytes, where L < 2^32 = 4.294.967.296 = 4.3gb
So for 80Mb page, you need a LONGTEXT. For PDF I would advice a LONGBLOB type, since this is binary format.
For the record: Eggyal has a point that it is better NOT to store this PDF in the database, but on disk. So I would advice on no doing it via the database, if you really need to put it in MySQL use a LONGBLOB
Check this link: http://dev.mysql.com/doc/refman/5.7/en/storage-requirements.html
TINYTEXT 256 bytes
TEXT 65,535 bytes ~64kb
MEDIUMTEXT 16,777,215 bytes ~16MB
LONGTEXT 4,294,967,295 bytes ~4GB