以下是MySQL中各字段的取值范围: TINYINT -128 - 127 TINYINT UNSIGNED 0 - 255 SMALLINT -32768 - 32767 SMALLINT UNSIGNED 0 - 65535 MEDIUMINT -8388608 - 8388607 MEDIUMINT UNSIGNED 0 - 16777215 INT 或 INTEGER -2147483648 - 2147483647 INT UNSIGN
以下是MySQL中各字段的取值范围:
TINYINT
-128 - 127
TINYINT UNSIGNED
0 - 255
SMALLINT
-32768 - 32767
SMALLINT UNSIGNED
0 - 65535
MEDIUMINT
-8388608 - 8388607
MEDIUMINT UNSIGNED
0 - 16777215
INT 或 INTEGER
-2147483648 - 2147483647
INT UNSIGNED 或 INTEGER UNSIGNED
0 - 4294967295
BIGINT
-9223372036854775808 - 9223372036854775807
BIGINT UNSIGNED
0 - 18446744073709551615
FLOAT
-3.402823466E+38 - -1.175494351E-38
0
1.175494351E-38 - 3.402823466E+38
DOUBLE 或 DOUBLE PRECISION 或 REAL
-1.7976931348623157E+308 - -2.2250738585072014E-308
0
2.2250738585072014E-308 - 1.7976931348623157E+308
DECIMAL[(M,[D])] 或 NUMERIC(M,D)
由M(整个数字的长度,包括小数点,小数点左边的位数,小数点右边的位数,但不包括负号)和D(小数点右边的位数)来决定,M缺省为10,D缺省为0
DATE
1000-01-01 - 9999-12-31
DATETIME
1000-01-01 00:00:00 - 9999-12-31 23:59:59
TIMESTAMP
1970-01-01 00:00:00 - 2037年的某天(具体是哪天我也不知道,呵呵)
TIME
-838:59:59' to 838:59:59
YEAR[(2|4)]
缺省为4位格式,4位格式取值范围为1901 - 2155,0000,2位格式取值范围为70-69(1970-2069)
CHAR(M) [BINARY] 或 NCHAR(M) [BINARY]
M的范围为1 - 255,如果没有BINARY项,则不分大小写,NCHAR表示使用缺省的字符集.在数据库中以空格补足,但在取出来时末尾的空格将自动去掉.
[NATIONAL] VARCHAR(M) [BINARY]
M的范围为1 - 255.在数据库中末尾的空格将自动去掉.
TINYBLOB 或 TINYTEXT
255(2^8-1)个字符
BLOB 或 TEXT
65535(2^16-1)个字符
MEDIUMBLOB 或 MEDIUMTEXT
16777215 (2^24-1)个字符
LONGBLOB 或 LONGTEXT
4294967295 (2^32-1)个字符
ENUM('value1','value2',...)
可以总共有65535个不同的值
SET('value1','value2',...)
最多有64个成员

MySQL'sBLOBissuitableforstoringbinarydatawithinarelationaldatabase,whileNoSQLoptionslikeMongoDB,Redis,andCassandraofferflexible,scalablesolutionsforunstructureddata.BLOBissimplerbutcanslowdownperformancewithlargedata;NoSQLprovidesbetterscalabilityand

ToaddauserinMySQL,use:CREATEUSER'username'@'host'IDENTIFIEDBY'password';Here'showtodoitsecurely:1)Choosethehostcarefullytocontrolaccess.2)SetresourcelimitswithoptionslikeMAX_QUERIES_PER_HOUR.3)Usestrong,uniquepasswords.4)EnforceSSL/TLSconnectionswith

ToavoidcommonmistakeswithstringdatatypesinMySQL,understandstringtypenuances,choosetherighttype,andmanageencodingandcollationsettingseffectively.1)UseCHARforfixed-lengthstrings,VARCHARforvariable-length,andTEXT/BLOBforlargerdata.2)Setcorrectcharacters

MySQloffersechar, Varchar, text, Anddenumforstringdata.usecharforfixed-Lengthstrings, VarcharerForvariable-Length, text forlarger text, AndenumforenforcingdataAntegritywithaetofvalues.

Optimizing MySQLBLOB requests can be done through the following strategies: 1. Reduce the frequency of BLOB query, use independent requests or delay loading; 2. Select the appropriate BLOB type (such as TINYBLOB); 3. Separate the BLOB data into separate tables; 4. Compress the BLOB data at the application layer; 5. Index the BLOB metadata. These methods can effectively improve performance by combining monitoring, caching and data sharding in actual applications.

Mastering the method of adding MySQL users is crucial for database administrators and developers because it ensures the security and access control of the database. 1) Create a new user using the CREATEUSER command, 2) Assign permissions through the GRANT command, 3) Use FLUSHPRIVILEGES to ensure permissions take effect, 4) Regularly audit and clean user accounts to maintain performance and security.

ChooseCHARforfixed-lengthdata,VARCHARforvariable-lengthdata,andTEXTforlargetextfields.1)CHARisefficientforconsistent-lengthdatalikecodes.2)VARCHARsuitsvariable-lengthdatalikenames,balancingflexibilityandperformance.3)TEXTisidealforlargetextslikeartic

Best practices for handling string data types and indexes in MySQL include: 1) Selecting the appropriate string type, such as CHAR for fixed length, VARCHAR for variable length, and TEXT for large text; 2) Be cautious in indexing, avoid over-indexing, and create indexes for common queries; 3) Use prefix indexes and full-text indexes to optimize long string searches; 4) Regularly monitor and optimize indexes to keep indexes small and efficient. Through these methods, we can balance read and write performance and improve database efficiency.


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

SublimeText3 English version
Recommended: Win version, supports code prompts!

SecLists
SecLists is the ultimate security tester's companion. It is a collection of various types of lists that are frequently used during security assessments, all in one place. SecLists helps make security testing more efficient and productive by conveniently providing all the lists a security tester might need. List types include usernames, passwords, URLs, fuzzing payloads, sensitive data patterns, web shells, and more. The tester can simply pull this repository onto a new test machine and he will have access to every type of list he needs.

Dreamweaver CS6
Visual web development tools

Notepad++7.3.1
Easy-to-use and free code editor

SublimeText3 Mac version
God-level code editing software (SublimeText3)
