case logic sleeves

8sdafasdf ' ++echo8sdafasdf++sed ' s/[0-9]//g ' +n1=sdafasdf+ ' [' -n sdafasdf '] ' +echo ' Pleaseinputanumber. ' Pleaseinputanumber.+exit1[[email protected]shell]#sh-xcase.sh+read-p ' Pleaseinputa number: ' nPleaseinputanumber:123 # #输入一个大于100的数字 + ' [' -z123 ' ++echo123++sed ' s/[0-9]//g ' +n1=+ ' [' -n ' ' ' + ' [' 123-lt60 '] ' + ' [' 123-ge60 '] ' + ' [ ' 123-lt80 ' ' + ' [' 123-ge80 '] ' + ' [' 123-lt 90 ' + ' [' 123-ge90 '] ' + ' [' 123-le100 '] ' + tag=0+

[ -n 01.sh ]; then echo ok; fiokWhat happens when the 3.-q file contains characters:[[emailprotected] shell]# if grep -wq ‘weixing01‘ /etc/passwd; then echo "sdjfk"; fisdjfkCase Judgment1. Scripting: [[emailprotected] shell]# cat case1.sh #!/bin/bashread-p "Please input a number:" Nif [-Z "$n"]then echo "Please input a number." Exit 1fin1= ' echo $n |sed ' s/[0-9]//g ' if [-N ' $n 1 "]then echo" please input a number. "Exit 1fiif [$n-lt] [$n-ge 0]then tag=1elif [$n-ge] [$n-lt +]then tag=

if logic judgment in shell scripts Logical judgment Expression: -GT (>); Greater than great than -lt ( If logical judgment format: Format 1:if condition; Then statement; Fi format 2:if condition; then statement; Else statement; Fi format 3:if ...; Elif ...; Then ...; else ...; Fi -- can use | | Combine multiple conditions a conditions b:a and b conditions a| | Condition b:a or b if [$a-gt 5] [$a-lt]; then if [$b-gt 5] | | [$b-lt 3]; Then F

a number:" NIf [-Z "$n"]Thenecho "Null,please input a number."Exit 1Exit 1 indicates the return value after executing the partial commandThat is, when the command finishes executing, use echo $? The valueFin1=echo $n | sed ‘s/[0-9]//g‘Change the number in variable N to null and assign to N1If [-N "$n 1"]Determines if the N1 is not empty, then outputs the following result, and is empty to continue executionThenecho "Please input a number."Exit 1FiIf [$n-lt] [$n-ge 0]ThenTag=1elif [$n-ge] [$n-L

The CASE expression returns a value based on the conditional logic. In the development process, we often need to return a value for a column based on the conditional logic. In this CASE, we need to use the CASE expression. For example, the following query of the Products tab

Tags: here Select traffic Results Isolation LEVEL SEL level size catIn general, database optimization can be divided into 4 aspects from the hardware level:CPU: That is, reduce the computational complexity, such as reducing the various types of SQL aggregation functions, window functions, case when and so on.IO: (Less access to data during query result set.) Data optimization from here to a great extentNetwork: Less query result set size, eliminate un

In our development process, we often need to return a value for a column, based on conditional logic, then we need to use the case expression. For example, the following query to the Products table uses a CASE expression in the SELECT statement to generate information that describes the value of the CategoryID column. The SQL code is as follows: --Setting