split用法 echo hello_xiao_lan | awk '{split($0,b,_);print b[3]}' //substr用法 awk '{a=substr($1,2);print a}' file2 //求均 awk '{ sum = $1sum ;count } END {print count, sum,sum/count}' aa.txt awk '{max=($2max?$2:max)} END {print max}' test.t
split用法echo "hello_xiao_lan" | awk '{split($0,b,"_");print b[3]}'
//substr用法
awk '{a=substr($1,2);print a}' file2//求均值
awk '{ sum = $1+sum ;count++ } END {print count, sum,sum/count}' aa.txt
awk '{max=($2>max?$2:max)} END {print max}' test.txt
分组求最大值
awk -F',' '{max[$1]=$2>max[$1]?$2:max[$1]} END {for (i in max) print i,max[i]}' t.txt
分组求和
awk -F',' '{sum[$1]=sum[$1]+$2} END {for (i in sum) print i,sum[i]}' t.txt
//传入变量
awk ' { if ($1 == "'$a'") print $0 }' test.txt
sub用法:
awk -F/ '{sub(/[a-z]+./,"",$3);print $3}' i.txt //用空替换掉连续字符串再加.(第一次匹配上的) 改成gsub所有的都替换掉
//包含某字符的行数
awk 'BEGIN {count=0} {if ($0~/hello/) count++} END {print count}' test.txt
//匹配再打印,两种写法
awk -F "|" '{if ($3~/cc/) print $0}' aa.txt
awk -F "|" '$3~/cc/ {print $0}' aa.txt
//next用法,如果调用next,那么next之后的命令就都不执行了
awk '{if(NR==1){next} print $1,$2}' data //第一行的数据不展示
awk -F" " '$1=="I0012"{next}{print $0}' file2
//getline用法,与next不同,当调用getline,后面的命令会执行,用下一行数据
awk -F" " '$1=="I0012"{getline;print $0}' file2
else用法
awk -F'|' '{if ($1 > 100) {print $1 ;} else {print "ok"}}' test1.txt
strftime用法
awk -F',' '{ if ($2=="98B8E35530AB") print $2,$3,$4,strftime("%Y-%m-%d %T",$5)}' test.log | head -3
//打印当前行号,及最后一列
echo "1234/1234/bb234xx/134" | awk -F/ '{print NR,$NF}'
//指定多个分隔符
awk -F'[ :/t]' '{print $1,$3}' test
//不是以hello开头的行
awk '!/^hello/' test.txt
//while用法
echo "1234/1234/bb234xx/134" | awk -F'/' '{ i=1;while(i
//for用法
echo "1234/1234/bb234xx/134" | awk -F'/' '{ for(i=1;i

TograntpermissionstonewMySQLusers,followthesesteps:1)AccessMySQLasauserwithsufficientprivileges,2)CreateanewuserwiththeCREATEUSERcommand,3)UsetheGRANTcommandtospecifypermissionslikeSELECT,INSERT,UPDATE,orALLPRIVILEGESonspecificdatabasesortables,and4)

ToaddusersinMySQLeffectivelyandsecurely,followthesesteps:1)UsetheCREATEUSERstatementtoaddanewuser,specifyingthehostandastrongpassword.2)GrantnecessaryprivilegesusingtheGRANTstatement,adheringtotheprincipleofleastprivilege.3)Implementsecuritymeasuresl

ToaddanewuserwithcomplexpermissionsinMySQL,followthesesteps:1)CreatetheuserwithCREATEUSER'newuser'@'localhost'IDENTIFIEDBY'password';.2)Grantreadaccesstoalltablesin'mydatabase'withGRANTSELECTONmydatabase.TO'newuser'@'localhost';.3)Grantwriteaccessto'

The string data types in MySQL include CHAR, VARCHAR, BINARY, VARBINARY, BLOB, and TEXT. The collations determine the comparison and sorting of strings. 1.CHAR is suitable for fixed-length strings, VARCHAR is suitable for variable-length strings. 2.BINARY and VARBINARY are used for binary data, and BLOB and TEXT are used for large object data. 3. Sorting rules such as utf8mb4_unicode_ci ignores upper and lower case and is suitable for user names; utf8mb4_bin is case sensitive and is suitable for fields that require precise comparison.

The best MySQLVARCHAR column length selection should be based on data analysis, consider future growth, evaluate performance impacts, and character set requirements. 1) Analyze the data to determine typical lengths; 2) Reserve future expansion space; 3) Pay attention to the impact of large lengths on performance; 4) Consider the impact of character sets on storage. Through these steps, the efficiency and scalability of the database can be optimized.

MySQLBLOBshavelimits:TINYBLOB(255bytes),BLOB(65,535bytes),MEDIUMBLOB(16,777,215bytes),andLONGBLOB(4,294,967,295bytes).TouseBLOBseffectively:1)ConsiderperformanceimpactsandstorelargeBLOBsexternally;2)Managebackupsandreplicationcarefully;3)Usepathsinst

The best tools and technologies for automating the creation of users in MySQL include: 1. MySQLWorkbench, suitable for small to medium-sized environments, easy to use but high resource consumption; 2. Ansible, suitable for multi-server environments, simple but steep learning curve; 3. Custom Python scripts, flexible but need to ensure script security; 4. Puppet and Chef, suitable for large-scale environments, complex but scalable. Scale, learning curve and integration needs should be considered when choosing.

Yes,youcansearchinsideaBLOBinMySQLusingspecifictechniques.1)ConverttheBLOBtoaUTF-8stringwithCONVERTfunctionandsearchusingLIKE.2)ForcompressedBLOBs,useUNCOMPRESSbeforeconversion.3)Considerperformanceimpactsanddataencoding.4)Forcomplexdata,externalproc


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