About mysql LPAD and substring function

concat means to assemble a string

lpad means padding character,

substring means to intercept the string

max indicates the maximum value of the field

 

lpad: padding character can pad the string, syntax lpad( string, padded_length, [ pad_string ] )

　　E.g

　　　　LPAD(
　　　　　　2,
　　　　　　8,
　　　　　　0
　　　　　　) means that the left side of 2 is filled with 8 0s

concat: concatenate strings concat ("1","2","3","4",'n'); n strings can be concatenated

concat('%',#{group_Desc},'%') After splicing ->%group_Desc%

max represents the maximum value of a field: