mysql - Why does UPDATE x SET y='c' AND TRUE result in y='0' -

-

i'm playing around sql challenge , noticed given table x single text column y following query:

update x set y='c' , true

results in y='0'

also:

update x set y='c' or true

results in y='1'

out of curiosity i'm trying understand what's happening underneath produce these results.

expressions y='c' , true , y='c' or true boolean expressions. evaluate either 1 when expression true, or 0, when expression false.

your update evaluates these expressions, , stores results in field y.


Comments

Post a Comment

Popular posts from this blog

c - Calling a function within a loop -

-
i trying simple addition function take number x array , add variable i it, iteration variable inside loop. instead of adding each variable individually , producing output of : 3, 2, 7 it produces values of 3, 5, 13. #include <stdio.h> int add(int x[], int y); int main(void) { int i; int a[3] = {3, 1, 5}; for(i=0; i<3; i++) { printf("%d \t", i); printf("%d, %d, equals %d \n", a[i], i, add(a[i], i)); } return 0; } int add(int x[], int y){ return x+y; } try int add(int x, int y){ return x+y; }
Read more

vb.net - Unbound DataGridView add row with checkbox error -

-
this windows forms program. have unbound datagridview control 4 columns; feature id string, parts string, flats string , showonest boolean. columns defined in form designer , boolean column is, indeed, set checkbox tristate set false. the user selects product list box , code executed populate grid grdfeat.rows.clear() = 0 curproduct.lstfeatures.count - 1 (curproduct.lstfeatures(i)) grdfeat.rows.add(.featureid, .parts, .flats, .showonest) end next if allowusertoaddrows false, everthing good. setting allowusertoaddrows true, however, results in following error: formatexception value '' cannot converted type 'boolean'. the error not triggered in code. it's displayed in new tab titled "no source available". it seems pretty clear process adds new editing row trying set checkbox string value, or perhaps null. i'm new (a few months) vb.net, suspect i'm overlooking simple setting somewhere, after several hours of trying...
Read more

How i fill combobox items in Radgridview manually using in vb.net -

-
how fill combobox items in radgridview manually without using datasource in vb.net have radgridview in form.(radgridview1) radgridview1 contained 3 column , column number 3 combobox type. want fill each combobox in column 3 data using code: unp ipe angle box other profile. don't know how it. you can use gridtemplatecolumn following. <telerik:gridtemplatecolumn itemstyle-wrap="true" itemstyle-verticalalign="middle" itemstyle-horizontalalign="center" allowfiltering="false" headerstyle-horizontalalign="center" headerstyle-width="3%" itemstyle-width="3%" headertext="profile"> <itemtemplate> <telerik:radcombobox> <items> <telerik:radcomboboxitem text="unp" value="unp" /> ...
Read more