The VARCHAR(MAX) type is a replacement for TEXT. The basic difference is that a TEXT type will always store the data in a blob whereas the VARCHAR(MAX) type will attempt to store the data directly in the row unless it exceeds the 8k limitation and at that point it stores it in a blob. Using … Read more
The max length of a varchar is subject to the max row size in MySQL, which is 64KB (not counting BLOBs): VARCHAR(65535) However, note that the limit is lower if you use a multi-byte character set: VARCHAR(21844) CHARACTER SET utf8 Here are some examples: The maximum row size is 65535, but a varchar also includes … Read more
You need ALTER TABLE YourTable ALTER COLUMN YourColumn <<new_datatype>> [NULL | NOT NULL] But remember to specify NOT NULL explicitly if desired. ALTER TABLE YourTable ALTER COLUMN YourColumn VARCHAR (500) NOT NULL; If you leave it unspecified as below… ALTER TABLE YourTable ALTER COLUMN YourColumn VARCHAR (500); Then the column will default to allowing nulls … Read more
Disk space is not the issue… but memory and performance will be. Double the page reads, double index size, strange LIKE and = constant behaviour etc Do you need to store Chinese etc script? Yes or no… And from MS BOL “Storage and Performance Effects of Unicode” Edit: Recent SO question highlighting how bad nvarchar … Read more
TEXT is used for large pieces of string data. If the length of the field exceeed a certain threshold, the text is stored out of row. VARCHAR is always stored in row and has a limit of 8000 characters. If you try to create a VARCHAR(x), where x > 8000, you get an error: Server: … Read more
Keep in mind that MySQL has a maximum row size limit The internal representation of a MySQL table has a maximum row size limit of 65,535 bytes, not counting BLOB and TEXT types. BLOB and TEXT columns only contribute 9 to 12 bytes toward the row size limit because their contents are stored separately from … Read more
TL;DR TEXT fixed max size of 65535 characters (you cannot limit the max size) takes 2 + c bytes of disk space, where c is the length of the stored string. cannot be (fully) part of an index. One would need to specify a prefix length. VARCHAR(M) variable max size of M characters M needs … Read more
It depends on how you format the Guid: Guid.NewGuid().ToString() = 36 characters (Hyphenated) outputs: 12345678-1234-1234-1234-123456789abc Guid.NewGuid().ToString(“D”) = 36 characters (Hyphenated, same as ToString()) outputs: 12345678-1234-1234-1234-123456789abc Guid.NewGuid().ToString(“N”) = 32 characters (Digits only) outputs: 12345678123412341234123456789abc Guid.NewGuid().ToString(“B”) = 38 characters (Braces) outputs: {12345678-1234-1234-1234-123456789abc} Guid.NewGuid().ToString(“P”) = 38 characters (Parentheses) outputs: (12345678-1234-1234-1234-123456789abc) Guid.NewGuid().ToString(“X”) = 68 characters (Hexadecimal) outputs: {0x12345678,0x1234,0x1234,{0x12,0x34,0x12,0x34,0x56,0x78,0x9a,0xbc}}
767 bytes in MySQL version 5.6 (and prior versions), is the stated prefix limitation for InnoDB tables. It’s 1,000 bytes long for MyISAM tables. This limit has been increased to 3072 bytes In MySQL version 5.7 (and upwards). You also have to be aware that if you set an index on a big char or … Read more
Just to clear up… or sum up… nchar and nvarchar can store Unicode characters. char and varchar cannot store Unicode characters. char and nchar are fixed-length which will reserve storage space for number of characters you specify even if you don’t use up all that space. varchar and nvarchar are variable-length which will only use … Read more